Methods for detecting neurological disorders

ABSTRACT

In one aspect, the present invention features methods for detecting at least one neurological disorder in a patient, the method comprising obtaining a biological sample from the patient; and detecting at least one aberrant human glutamate transporter 2 (EAAT 2) mRNA in the sample as being indicative of the neurological disorder in the patient. In a particular aspect, the invention is useful for detecting amyotrophic lateral sclerosis (ALS) in the patient.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention features methods for detecting at least onespecified neurological disorder in a subject. In one aspect, theinvention relates to novel polynucleotides for detecting theneurological disorder. In a related aspect, the invention providesmethods for identifying, analyzing, and using the polynucleotides.Further provided are screening methods for detecting therapeuticcompounds with capacity to treat the neurological disorder. The presentinvention has a variety of uses including detecting a specified motorneuron disorder in a patient.

2. Background

Neurological disorders can significantly impact the central nervoussystem (CNS) and motor neuron units. For example, certain neurologicaldisorders of the CNS are known to adversely affect the brain andassociated structures. Neurological disorders affecting motor neuronunits have been grouped into motor neuron diseases and peripheralneuropathies. See generally Kandel, E. R. et al; (1991) in Principles ofNeuroscience, Appleton & Lange, Norwalk, Conn.; and Rowland, L. P. (ed.)(1982) in Human Motor Neuron Diseases. New York. Raven Press.

An illustrative motor neuron disease is amyotrophic lateral sclerosis(ALS). ALS has been reported to be a chronic neuromuscular disorderhaving recognized clinical manifestations. For example, it has beensuggested that degeneration of cortical and spinal/bulbar motor neuronsmay play a key role in the disorder. ALS is nearly always fatal. About95% of all ALS cases are sporadic, with many of the remaining casesshowing autosomal dominant inheritance. See e.g., Kunc R. W. et al.,(1992) Motor Neuron Diseases In Diseases of the Nervous System, Asburyet al. eds. (Philadelphia W. B. Saunders) pp. 1179-1208; Brown, R. H.,(1996) Amer. Neurol. 30:145; Siddique, T. and Deng., H. X. (1996) Hum.Mol. Genetics 5:1465).

Specific CNS disorders have been also described. In particular, somehave been attributed to cholinergic, dopaminergic, adrenergic,serotonergic deficiencies or combinations thereof. CNS disorders ofsevere impact include pre-senile dementia (sometimes referred to asAlzheimer's disease (AD) or early-onset Alzheimer's disease), seniledementia (dementia of the Alzheimer's type), Parkinson's disease (PD),and Huntington's disease (HD, sometimes referenced as Huntington'schorea). Such CNS disorders are well-represented in the humanpopulation. See generally; Gusella, J. F. et al. (1983) Nature 306: 234;Borlauer. W. and Jprmuloewoca. P. (eds.) (1976); Adv. in Parkinsonism:Biochemistry, Physiology, Treatment. Fifth International Symposium onParkinson's Disease (Vienna) Basel: Roche; and references cited therein.

Significant attention has been directed towards understanding theetiology of motor neuron diseases. For example, abnormal levels ofcertain excitotoxic neurotransmitters have been reported to adverselycontribute to many motor neuron diseases. In particular,glutamate-mediated excitotoxicity is recognized to have a critical rolein ALS. See e.g., Rothstein J. D. et al., (1990) Ann. Neurol. 28: 18. ;Rothstein J. D. et al. (1992) N. Engl. Med. 326: 1464; Rothstein J. D.et al. (1993) PNAS (USA) 90: 6591; and Lacomblez, L. et al., (1996)Lancet 347: 1179.

There has been substantial efforts towards understanding mechanisms forreducing glutamate levels in the nervous system. For example,high-affinity, sodium-dependent glutamate transport is one reportedmeans of inactivating glutamate. In particular, astrocytic excitatoryamino acid transporter 2 (EAAT 2) proteins are believed to havesubstantial functions in that inactivation. See e.g., Rothstein J. D. etal. (1994) Neuron 28: 18; Rothstein J. D. et al., (1995) Ann. Neurol.38: 78. and references cited therein.

In particular, investigations have suggested that EAAT 2 is apredominant glutamate transporter. More particularly, certain antisenseknockdown studies have been reported to demonstrate that EAAT 2 loss canlead to excitotoxic neuronal degeneration and progressive motorimpairment. Studies of ALS and other neurodegenerative disorders haverelated impaired glutamate transport to loss of the EAAT 2 protein. Inparticular, up to 60% to 70% of the sporadic ALS patients examined havea 30% to 95% loss of the EAAT 2 protein. See e.g., Haugeto et al.,supra; Rothstein J. D., et al., (1996) Neuron 16: 675; Bristol, L. A.and Rothstein, J. D. (1996) Ann. Neurol. 39: 676.

There have been attempts to treat or prevent neurological disorders ofthe CNS and the motor neuron units. However, most existing therapies donot always stem the development or severity of the disorders inafflicted patients. See e.g., Rowell, (1987) Adv. Behav. Biol. 31: 191;Rinne, et al. Brain Res. (1991) 54: 167; U.S. Pat. No. 5,210,076 toBerliner; Yurek, D. M. (1990) Ann. Rev. Neurosci. 13: 415, and Rowlandet al. supra.

Substantial research effort has focussed on developing effective methodsfor detecting neurological disorders in patients. However, many existingmethods are not always effective or reliable. For example, some methodsare optimized to analyze post-mortem samples. Such methods providelittle benefit for the afflicted patient. Other methods rely on testingliving patients for specific cognitive or motor skills. However, suchtests can be difficult to perform or interpret in some settings.

Accordingly, there is a need in the field for effective and reliablemethods for detecting neurological disorders in a living patient. Thereis general recognition that such methods would positively impact manyexisting therapies. It would be particularly desirable to have methodsfor detecting specific neurological disorders in a living patient beforedisease onset or at an early stage of disease progression.

SUMMARY OF THE INVENTION

The present invention features methods for detecting at least onespecified neurological disorder in a subject. In one aspect, the methodsinclude obtaining a biological sample from the subject and detecting atleast one type of aberrant human glutamate transporter 2 mRNA in thesample. Presence of the aberrant mRNA is indicative of the neurologicaldisorder in the subject. The invention also relates to novelpolynucleotides that can be used to detect the neurological disorder.Further provided are methods for isolating a variety of aberrant humanglutamate transporter 2 polynucleotides. The invention also providesscreening methods for detecting compounds useful in the diagnosis ortreatment of specified neurological disorders. The present invention hasa variety of uses including monitoring efficacy of a therapy fortreating the neurological disorder.

In general, we have discovered aberrant human glutamate transporter 2mRNAs in patients suffering from or suspected of suffering from aspecific neurological disorder. It was found that incidence of theaberrant mRNAs substantially increased in affected nervous systemregions. For example, incidence of the aberrant mRNAs could be detectedin patients afflicted with a specific motor neuron disease.Significantly, the present invention provides sensitive and reliablemethods for detecting specific neurological disorders in living patientswith minimal impact to the nervous system.

The term “human glutamate transporter 2” is sometimes abbreviated hereinas “EAAT 2”. The term “EAAT 2” will be particularly used to refer to thehuman astroglial glutamate transporter 2 gene as well as normal oraberrant polynucleotides derived from that gene.

As will be discussed more fully below, aberrant EAAT 2 polynucleotidesof this invention are novel molecular markers that can be used to detectspecific neurological disorders. In particular, aberrant EAAT 2 mRNAs ofthis invention are intron-retention or exon-skipping variants of normalEAAT 2 mRNA. The aberrant EAAT 2 mRNAs were found in a majority ofpatients that were known to have or were suspected of having a specifiedneurological disorder. However, the aberrant EAAT 2 mRNAs were not foundin control samples obtained from apparently healthy and non-affecteddonors. Accordingly, detection of at least one type of aberrant EAAT 2mRNA in the patient is taken to be indicative of the neurologicaldisorder in that patient.

The neurological disorders that can be detected in accord with thepresent invention include specific disorders that have been reported tobe associated with excitotoxicity. Particularly included are specifiedneurological disorders affecting motor neuron function. Specificallyincluded are neurological disorders impacting the CNS or motor neuronunits such as amyotrophic lateral sclerosis (ALS), Huntington's disease(HD), Parkinson's disease (PD), and Alzheimer's disease (AD). As will bepointed out below, in selected disorders, at least one type of aberrantEAAT 2 mRNA has been detected in a majority of patients that have orwere suspected of having the disorder. As noted, those aberrant mRNAswere not detected in apparently healthy and non-affected donors.

The present invention has a number of important advantages. For example,the invention can be used to detect a specified neurological disorder ina living patient with minimal impact to the nervous system. For example,one embodiment of the present invention features a method for detectingat least one type of aberrant EAAT 2 mRNA in a replaceable nervoussystem fluid that can be readily obtained from the patient. In thisembodiment, presence of at least one type of aberrant EAAT 2 mRNA in thefluid is indicative of the neurological disorder in that patient.

In some instances, the patient to be tested may not yet manifest overtsigns of any neurological disorder. In this instance, the methods of theinvention can serve as an indicator of predisposition for orsusceptibility to the disorder. In contrast, many prior methods fordetecting neurological disorders rely on difficult cognitive or motortests. Other more definitive tests are typically formatted tocharacterize post-mortem nervous system tissue. Unlike these priormethods, the present invention provides reliable and sensitive methodsfor detecting neurological disorders while the patient is living.Significantly, opportunities for early medical intervention areincreased by practice of the invention.

In one aspect, the present invention provides an assay-method fordetecting at least one specified neurological disorder in a patient whohas or is suspected of having that neurological disorder. The methodgenerally involves obtaining a biological sample from the patient anddetecting at least one type of aberrant EAAT 2 mRNA in the sample asindicative of the neurological disorder. In one embodiment of themethod, detection of the aberrant EAAT 2 mRNA is achieved by amplifyingthe sample in a polymerase chain reaction (PCR) or suitable relatedmethod. Typically, the amplification method selected will be sufficientto make complementary polynucleotides, typically complementary DNA(cDNA), from the sample. That is, the PCR or related method is used tomake nucleic acid copies of the mRNA which copies are usually cDNAcopies but can be at least partially RNA copies (cRNA) in someinstances. A preferred amplification method is a reversetranscriptase-PCR (RT-PCR) method using at least two oligonucleotideprimers. In a particular embodiment, amplified cDNA made from aberrantEAAT 2 mRNA (if present in the sample) is sequenced and the resultingDNA sequence is compared to the sequence of the normal EAAT 2 cDNA(FIGS. 1A-C and SEQ ID NO: 1). The comparison allows determination ofthe aberrant EAAT 2 mRNA structure in most instances. In many cases, asuitable control sample is included to provide suitable co-amplificationof normal EAAT 2 mRNA. Preferred control samples generally provide abaseline for any basal expression of the normal EAAT 2 mRNA. In anotherparticular embodiment, DNA sequence from the cDNA is substantiallyhomologous or identical to specific aberrant EAAT 2 cDNA sequencesdisclosed below.

In another aspect of the present invention, assay methods are providedfor detecting the neurological disorder in the patient in which aberrantEAAT 2 mRNA is detected by making a polynucleotide library from thebiological sample. In one embodiment, the polynucleotide library is acDNA library and the methods include detecting in the library at leastone nucleic acid that includes a sequence substantially homologous oridentical to specified aberrant EAAT 2 cDNA sequences disclosed below.

Further provided by the present invention are methods for detecting atleast one specified neurological disorder in the patient in which themethods involve obtaining a first biological sample from a suitablecontrol donor and a second biological sample from the patient,amplifying nucleic acid in the samples independently, and detecting inthe second sample any amplified nucleic acid as indicative of theneurological disorder in the patient. In one embodiment of the method,mRNA in the first and second samples is independently amplified underconditions capable of producing cDNA from at least one type of aberrantEAAT 2 mRNA (if present) in the sample. In this embodiment, the aberrantmRNA includes intron sequence from the EAAT 2 gene. The method isespecially useful for detecting specific aberrant EAAT 2 mRNAs whichretain at least one intron or intron fragment from the EAAT 2 gene.Presence of a suitable amplification product in the second sample, whencompared to the first sample (control), is an indication of theneurological disorder in the patient.

It will be appreciated that in instances where a baseline level ofnormal EAAT 2 gene expression has been established in the control donoror group of such donors it will not always be necessary to obtain thefirst biological sample; In such cases, the method can be performed bymanipulating the second sample and comparing results obtained from thesecond sample to the baseline.

The present invention provides additional methods for detecting at leastone specified neurological disorder in the patient which includesobtaining a first biological sample from a control donor and a secondbiological sample from the patient and detecting at least one type ofaberrant EAAT 2 mRNA in the second sample. In one embodiment, nucleicacid in the first and second samples is independently amplified underconditions capable of producing complementary nucleic acid from themRNA, typically cDNA. In this embodiment, presence of at least oneamplification product in the second sample that is substantially smallerthan its corresponding amplification product in the first sample isindicative of the neurological disorder in the patient. That is,presence of an amplification product in the second sample which hasfewer nucleotides than the corresponding amplification product in thefirst sample is an indicator of the disorder. That determination can bemade by standard nucleic acid sizing manipulations such as those foundbelow. The method is particularly useful for detecting exon-skippingEAAT 2 mRNAs in the second sample. More particularly, the method isuseful for identifying aberrant EAAT 2 mRNAs that are missing at least afragment of an EAAT 2 gene exon up to an entire exon and including lossof multiple exons. The multiple exons can be contiguous ornon-contiguous with respect to the normal EAAT 2 gene.

As noted above, in some instances it will not be necessary to obtain thefirst biological sample in cases where a suitable baseline of normalEAAT 2 gene expression has been established.

Additionally provided are methods for detecting at least one specifiedneurological disorder in the patient which methods include obtaining abiological sample from the patient and detecting at least one type ofaberrant human EAAT 2 mRNA in the sample. In one embodiment, the methodincludes contacting the sample with a nucleic acid that includessequence complementary to at least a fragment of an EAAT 2 gene intronup to an entire intron. Generally, the contact will be under conditionsconducive to forming a specific binding complex between the nucleic acidand any aberrant EAAT 2 mRNA in the sample. Preferred use of the methodrequires that the aberrant EAAT 2 mRNA in the sample include a retainedintron or a retained fragment of the intron. In this method, detectionof the specific binding complex is indicative of the neurologicaldisorder in the patient.

In a particular embodiment of the method, detection of the specificbinding complex can be achieved by one or a combination of differentstrategies including treating the binding complex with a nuclease,typically a single-strand nuclease, and then identifying any hydrolyzednucleic acid in the binding complex as indicative of the neurologicaldisorder. Alternatively, the detection can be achieved by standardhybridization techniques such as those specified below.

Preferred use of the present methods will typically include RT-PCRamplification of specified nucleic acid sequence in biological samplesof interest, although other PCR methods or recombinant methods such ascloning can be used in some instances for the amplification.Additionally, it is generally preferred that the biological samplesinclude detectable levels of RNA; preferably mRNA; and more preferablynormal EAAT 2 mRNA, aberrant EAAT 2 mRNA, or both. Additionallypreferred is use of a biological sample that includes or consists of areplaceable nervous system fluid, preferably cerebrospinal fluid (CSF)which when taken from the patient will, by conventional medicalprocedures, minimally impact the nervous system. However in otherembodiments of the invention, biological samples such as nervous systemtissue samples, e.g., biopsies, tissue slices and the like can be usedin some instances. Additionally preferred is use of the presentinvention to detect specific neurological disorders (ALS, AD, HD andPD). A particularly preferred neurological disorder for purposes of thisinvention is ALS.

The invention further provides methods for isolating an aberrant EAAT 2polynucleotide which methods generally include obtaining a firstbiological sample from a control donor and a second biological samplefrom the patient. In one embodiment, the RNA samples include detectableamounts of RNA and particularly mRNA, and the method involves makingcDNA in each of the first and second samples. Production of the cDNA canbe accomplished by nearly any suitable method including PCR andparticularly RT-PCR using at least two specified oligonucleotideprimers. In this method, a first portion of the cDNA is introduced intosuitable control cells under culture conditions sufficient to expressthe cDNA in the control cells. A second portion of the cDNA isintroduced into suitable test cells under the same or closely relatedconditions. The test and control cells are then independently assayedfor glutamate transport as discussed below.

Reference herein to a “standard glutamate transport” assay or similarterm is meant to denote a preferred assay for detecting glutamatetransport in suitable cultured cells. In particular, a substantialreduction in glutamate transport in the test cells described above isindicative of presence of at least one type of aberrant EAAT 2 cDNA inthe second sample. Preferably, the glutamate transport is reduced in thetest cells (relative to the control cells) by at least about 10%, morepreferably at least about 20%, 30%, or about 40%, and still morepreferably at least about 50%, 60%, 70%, 80%, 90%, or 99% or more up toabout 100% relative to glutamate transport in the control cells.

In a particular embodiment of the method, cDNA produced from the firstand second samples is co-introduced into the test cells, e.g., bycombining the cDNA from each of the samples prior to theco-introduction. The test cells are subsequently cultured underconditions sufficient to express each of the cDNAs in the test cells.The test cells and control cells are then independently assayed toanalyze glutamate transport, e.g., in the standard glutamate transportassay. A substantial reduction or absence of glutamate transport in thetest cells is indicative of presence of at least one type of aberranthuman EAAT 2 cDNA in the second sample.

As will be explained more fully in the discussion that follows, it hasbeen found that specific aberrant EAAT 2 cDNAs of this invention, whenexpressed in suitable test cells, are capable of significantlydecreasing or eliminating expression from the co-introduced normal EAAT2 cDNA. That reduction can be detected and quantified if desired byseveral means including conducting the standard glutamate transportassay described below. Decreased expression of the normal EAAT 2 gene(or introduced cDNA) will sometimes be referred to as “dominantdown-regulation” or a related term to denote capacity of the aberrantEAAT 2 cDNA to decrease expression of the normal EAAT 2 gene or (cDNA).A specific aberrant EAAT 2 cDNAs with such capacity is described below.

As will be fully appreciated, it will not always be necessary to obtainthe first biological sample from the control donor or to make thecontrol cells in instances where a suitable baseline level of glutamatetransport has already been established.

As noted, the methods of the present invention are highly useful fordetecting at least one or specified neurological disorder in a patient,which patient has or is suspected of having the neurological disorder.In one embodiment, the invention can be employed to confirm presence ofthe neurological disorder. In a particular embodiment more specificallydescribed below, the present invention embraces certain hybridizationchips that can be employed to detect the neurological disorder.

In another embodiment, the invention can be used to evaluate efficacy ofa therapy employed to treat a patient suffering from a specifiedneurological disorder such as ALS. In this embodiment, levels of normalEAAT 2 protein, mRNA, or both are determined in a biological sampleobtained from the patient before (control), during, and/or followingtreatment. An increase in the level of the normal protein, mRNA (orboth) will be indicative of efficacious therapy. Preferred are therapiesformatted to treat ALS and particularly therapies including orconsisting of administration of Rilutek™ (riluzole).

The present invention further pertains to a polynucleotide (RNA, mRNA,cDNA, genomic DNA, or a chimera thereof) that includes or consists of anisolated nucleic acid that encodes an aberrant EAAT 2 mRNA or thecomplement thereof (RNA, DNA, or a chimera thereof). In one embodiment,the isolated nucleic acid includes a DNA complement of the aberrant EAAT2 mRNA which complement can be cDNA. The polynucleotide can be derived(whole or in part) from a variety of sources, e.g., by amplifying abiological sample of interest. In a particular embodiment, theamplification is suitably conducted by PCR or a related method withRT-PCR being a preferred amplification method.

In one embodiment, the isolated nucleic acid is preferably inserted intoa suitable recombinant vector such as a suitable recombinant DNA vector.It is preferred that the vector be capable of propagating the nucleicacid in a suitable prokaryotic or eukaryotic host cell. Additionallypreferred recombinant vectors are capable of expressing that isolatednucleic acid as RNA and preferably mRNA, in a suitable cell expressionsystem. The recombinant vector typically includes control elementsoperably linked to the inserted nucleic acid (e.g., promoter, leader,and/or enhancer elements) which control elements can be selected tooptimize replication and/or transcription of the vector in the cells.

Polynucleotides of the invention generally include an isolated nucleicacid sequence that encodes an aberrant EAAT 2 mRNA of this invention orthe complement thereof. In one embodiment, the polynucleotides includean isolated nucleic acid sequence that is substantially homologous to atleast one aberrant EAAT 2 cDNA. See in the drawings below and SEQ ID NOS3 & 5-13, respectively, in order of appearance (inclusive). In aspecific embodiment, the isolated nucleic acids include or consists ofcDNA and have a length of between about 50 to about 100 nucleotides,about 100, 200, 500, 1000, 2000 to about 2500 nucleotides, as determinedby standard nucleic acid sizing methods as disclosed below. In anotherembodiment, the isolated nucleic acid includes or consists of RNA andparticularly mRNA that is also substantially homologous to the specificcDNA sequences and which have having substantially the same length asthe cDNA.

Particularly preferred are the aberrant EAAT 2 cDNA sequencesspecifically shown in the drawings and in SEQ ID NOS 3 & 5-13,respectively, in order of appearance. Additionally preferred are thosesequences that are capable of significantly reducing glutamate transportin the standard glutamate transport assay. For example, specific use ofthe standard glutamate transport assay includes co-introduction insuitable cells of the aberrant EAAT 2 cDNA sequence with the normal EAAT2 cDNA (SEQ ID No. 1) or a suitable fragment thereof. Preferably, theaberrant EAAT 2 cDNA sequence is capable of reducing the glutamatetransport in the cells by at least about 10%, preferably at least about20%, 30%, or about 40%, more preferably about 50%, 60%, 70%, 80%, 90%,99% or more up to about 100% relative to glutamate transport in asuitable control assay.

Additionally preferred are complement sequences (DNA or RNA) at leastsubstantially homologous and preferably identical to the DNA sequencesshown in SEQ ID NOS 3 & 5-13, respectively, in order of appearance.

As will become more apparent below, many aberrant EAAT 2 polynucleotidesof the invention are not capable of producing significant levels ofpolypeptide under most conditions. However in some cases, significantamounts of the polypeptide may be produced from a particularpolynucleotide of interest. That polypeptide can be at least partlyfunctional and may be almost totally functional as determined by thestandard glutamate transport assay. For example, the polypeptide willexhibit at least about a 50%, 60%, 70%, or at least about an 80%, up toat least about a 90% or at least about a 95% or more reduction inglutamate transport when compared to a suitable control. Thepolypeptides will sometimes be referred to herein as a “aberrantpolypeptides” or a related tenm to denote less than about 100% of theactivity of the normal EAAT 2 polypeptide.

Additionally provided are antibodies (polyclonal and monoclonal) thatare capable of specifically binding to an aberrant polypeptide.

Further provided are cultured host cells which have been transformed,transfected or infected either transiently or stably by at least onerecombinant vector of the invention which vector includes an isolatednucleic acid that is capable of encoding an aberrant EAAT 2 mRNA of thecomplement thereof (DNA or RNA).

The present invention also provides useful oligonucleotide primers,typically single-stranded primers, which oligonucleotide primers arecomplementary to an RNA splice junction of an aberrant EAAT 2polynucleotide. As will be shown in the discussion and drawings whichfollow, an RNA splice junction is typically referenced with respect to acDNA sequence. Preferred are RNA splice junctions that are unique to anaberrant EAAT 2 cDNA and are not found in the normal EAAT 2 cDNAsequence (FIGS. 1A-C and SEQ ID NO. 1). Accordingly, the oligonucleotideprimers will not usually hybridize to a normal EAAT 2 gene, cDNA or mRNAsequence under normal hybridization conditions specified below. Theoligonucleotide primers can be employed, e.g., to detect or amplify anaberrant EAAT 2 mRNA of interest.

Additional polynucleotides of the present invention have important uses.For example, the invention provides for recombinant vectors that includean isolated nucleic acid as discussed. The recombinant vectors can beused to produce significant amounts of nucleic acid sequence that can besense or anti-sense, single-stranded or double-stranded. Generally,normal mRNA transcribed from DNA is referred to as the “sense” RNAstrand and oppositely oriented RNA is termed antisense RNA. Antisensepolynucleotides, then, refer to sequences of DNA or RNA which can bindin a Watson-Crick fashion to a sequence on a target mRNA. See generallyBentley, D. L. and Groudine, M. (1986) Nature 321:702; and Kimelman, D.Gene regulation: Biology of Antisense RNA and DNA, R. P. Erickson, J. G.Izant, eds. (Raven Press, New York).

Aberrant EAAT 2 mRNA in a biological sample will sometimes be referredto herein as a “target” to denote potential for specific binding betweena polynucleotide of interest, e.g., a suitable anti-sense RNA, and theaberrant EAAT 2 mRNA in the sample.

In one preferred embodiment, the recombinant vectors include DNAsequences that encode an anti-sense RNA which RNA is substantiallyhomologous to specified aberrant EAAT 2 cDNA sequences described below.In this instance it will be understood that the anti-sense RNA willusually include a uracil (U) in place of thymidine (T) where the cDNAsequence has a thymidine. In a preferred embodiment, the anti-sense RNAhas a length of at least about 20 to about 50 nucleotides, at leastabout 100 to about 250 nucleotides, at least about 300 to about 700nucleotides, or at least about 1000 to about 2000 and up to about 2500nucleotides as determined by standard polynucleotide sizing methods. Inmost cases, the length of the anti-sense RNA will be guided by intendeduse including the length of the target.

The antisense RNA encoded by specific recombinant vectors of thisinvention is usually designed to undergo complementary base pairing(hybridization) with the target, rendering the target essentiallyunavailable for translation in most cases. In some instances, theantisense RNA will render the target susceptible to degradation, therebysubstantially reducing the amount of the target in relevant cells ortissue. Accordingly, the recombinant vectors of the invention can beused to control undesired aberrant EAAT 2 mRNA in the cells or tissue.

Specific recombinant vectors of this invention that are capable ofproducing anti-sense RNA complementary to a specific aberrant EAAT 2mRNA (or more than one of such mRNA) can be used therapeutically toreduce levels of the target in vivo or in vitro. For example, in oneembodiment, a desired recombinant vector is administered to a patient inneed of reduced levels of the target. In this case, the administrationis sufficient to reduce levels of the target mRNA in the patient.Presence of the anti-sense RNA in the cells or tissue can in somesettings boost expression of the normal EAAT 2 gene therein. Thatincrease in expression can be monitored by a spectrum of tests includingthe standard glutamate transport assay.

In another embodiment, the recombinant vector is formatted to produceanti-sense DNA of about the same size as the anti-sense DNA.

In addition, the polynucleotides of this invention and particularly theisolated nucleic acids and recombinant vectors described herein can beused as important controls for detecting and analyzing normal andaberrant EAAT 2 gene expression in vitro and in vivo.

Additionally provided by the present invention is a solid support towhich has been bound at least one of specified polynucleotide of thisinvention. In another embodiment, a plurality of specifiedpolynucleotides, the same or different, are bound to the solid support.In a particular embodiment, the solid support is a hybridization chip(sometimes referred as a “micro-chip” or like term) that is capable ofdetecting at least one aberrant EAAT 2 polynucleotide, typically anaberrant EAAT 2 mRNA in a biological sample obtained from a patient.

Further provided are methods for isolating a nucleic acid andparticularly a cDNA that is complementary to at least one aberrant EAAT2 mRNA of this invention. The methods generally involve obtaining asuitable biological sample from a patient and preparing cDNA from thesample. Preparation of the cDNA can be achieved by several methodsincluding PCR and particularly RT-PCR. The cDNA produced can be purifiedif needed and can be inserted into a suitable recombinant vector bystandard techniques. Alternatively, the cDNA can be used in linear form,e.g., as a detectably-labeled probe, without insertion into therecombinant vector.

Recombinant vectors of the invention can be introduced into suitablecells or groups of such cells including tissue or organs if desiredeither in vitro or in vivo. Preferably the cells are capable ofexpressing the recombinant vector at detectable levels. Host cellscomprising the vectors can be cultured in medium capable of supportingpropagation and/or expression of the vectors in the cells. The cells canbe eukaryotic cells, preferably mammalian cells, that are capable ofexpressing desired sequences in the recombinant vector. In someinstances it will be desirable to introduce the vector into a suitableprokaryotic host e.g., bacteria to propagate the vector.

Isolated nucleic acids and polypeptides of the invention can be obtainedas a substantially pure preparation if desired. That is, the nucleicacids and polypeptides can be isolated in substantially pure form bystandard methods and can be provided as sterile preparations if desired.Methods for providing substantially pure preparations of nucleic acidsand polypeptides are discussed below.

Additionally provided are methods for identifying a compound useful inthe treatment or diagnosis of at least one of the neurological disordersspecified herein. In one embodiment, the method includes contacting asuitable cultured cell with at least one candidate compound anddetecting an increase in normal EAAT 2 polypeptide activity asindicative of the compound. Typically, the cultured cell will include atleast one aberrant EAAT 2 polynucleotide, e.g., mRNA. It is generallypreferred that the cultured cell be capable of expressing normal EAAT 2mRNA, e.g., by methods involving transient or stable expression of thenormal EAAT 2 cDNA (FIG. 1 and SEQ ID NO 1). Alternatively, the culturedcell may naturally express the normal EAAT 2 gene at suitable levels. Ina particular embodiment, the cultured cell includes at least oneaberrant EAAT 2 cDNA that is capable of being expressed at the mRNA orprotein level in the cultured cell.

In preferred embodiments, the compound is capable of boosting expressionof the normal EAAT 2 polypeptide by at least about 20%, at least about30% to about 50%, preferably at least about 60%, 70%, 80%, 90%, or about100% or more (relative to a suitable control) as determined, e.g., by aWestern blot or by the standard glutamate transport assay. Additionallypreferred are compounds that are capable of increasing normal EAAT 2mRNA levels by at least about 10%, preferably at least about 20%, 30%,40% to about 50%, more preferably at least about 60%, 70%, 80%, 90%, orabout 100% or more relative to a suitable control as determined, e.g.,by quantitative PCR or Northern blots.

The invention further provides methods for treating or preventing aneurological disorder in a patient. In one embodiment, the methodincludes administering to the patient a therapeutically effective amountof a recombinant vector of the invention which is capable of expressinganti-sense mRNA that can specifically bind target. The recombinantvector can be administered to the patient either as the sole activeagent or in combination with other agents including additionalrecombinant vectors as provided herein.

Additionally provided are kits useful in the detection or treatment ofat least one specific neurological disorder in a patient.

The invention also features a polynucleotide library including nucleicacid sequence encoding a sequence substantially homologous or identicalto at least one of the aberrant EAAT 2 polynucleotides disclosed herein.

All documents disclosed herein are incorporated by reference in theirentirety. The following non-limiting examples are illustrative of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-C show the sequence of the human astrocytic EAAT 2 cDNA andpolypeptide sequence (SEQ ID NOS 1 & 2).

FIGS. 2A-B show the sequence of an aberrant EAAT 2 cDNA sequence, with aretained intron sequence (SEQ ID NOS 3 & 4).

FIG. 3 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 5).

FIG. 4 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 6)

FIG. 5 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 7).

FIG. 6 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 8).

FIG. 7 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 9).

FIG. 8 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 10).

FIG. 9 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 11).

FIG. 10 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 12).

FIG. 11 is a drawing showing an aberrant EAAT 2 cDNA sequence withskipped exon sequence (SEQ ID NO: 13).

FIG. 12 is a table showing exon positions, RNA splice acceptor sequences(SEQ ID NOS 24-33 respectively, in order of appearance) and RNA splicedonor sequences (SEQ ID NOS 34-43 respectively, in order of appearance)of the normal EAAT 2 gene sequence.

FIG. 13A is a schematic drawing showing some aberrant EAAT 2 mRNAs inrelation to the normal EAAT 2 gene sequence. Numbered boxes representindividual exons. The connected arrow heads indicate the primer regionsused for RT-PCR. The hatched bars indicate the regions used to prepareprobes for in situ hybridization. The triangle indicates a Hind III siteused as an insertion site for constructing an internal control plasmidpE2F.

FIG. 13B is a schematic drawing showing sequence analysis of truncatedEAAT 2 transcripts (SEQ ID NOS 44-59, respectively, in order ofappearance). It will be appreciated that each of the sequences shown(sometimes referenced as B₁ to B₈) are representative of largersequences (see FIGS. 3-11 and SEQ ID NOS 5-13, respectively, in order ofappearance). In the right panel, twenty nucleotides on both sides ofeach internal deletion transcript are displayed. Arrows indicatesplicing junctions. Sequences between the arrows are spliced out. Dashedlines indicate nucleotides within the deleted sequences. A schematicrepresentation of the deleted regions is presented in the right panel.Cross-hatched boxes represent regions of missing RNA sequence.

FIG. 14A is a representation of a Western blot and a Southern blot ofRT-PCR reactions. The figure shows that aberrant mRNA species arepresent in ALS, but not control motor cortex.

FIG. 14B is a representation of a Southern blot of RT-PCR reactions. Theblot shows an aberrant mRNA species in ALS but not control motor cortex.

FIG. 14C is a representation of a Southern blot of RT-PCR reactions. Theblot shows truncated EAAT 2 transcripts in ALS but not control motorcortex. Lanes numbers are identical to patients labeled in FIG. 1A.

FIG. 14D is a representation of a Southern Blot of RT-PCR reactions. Theblots show no aberrant EAAT1 or SMN transcripts were found in ALS motorcortex. Lanes numbers are identical to patients labeled in FIG. 13A.

FIGS. 15A-15H are representations of in situ hybridization of partialintron 7-retention mRNA in motor cortex. Immunohistochemistry and insitu hybridization studies were performed on 3 different specimens.Scale bar for A, B, C, G, H=0.1 mm; scale bar for D, E, F=0.01 nm.

FIG. 16A is a representation of a Southern blot of RT-PCR reactions. PCRreaction products from different amplification cycles were subjected toSouthern blot analysis using an oligonucleotide probe located 3′ end ofthe PCR fragment. wt, wild-type EAAT 2; tr-1 and tr-2, two truncatedaberrant species.

FIG. 16B is a graph showing quantitative analysis of aberrant EAAT 2mRNA in ALS motor cortex.

FIG. 16C is a representation of a Southern blot of an SI nucleaseanalysis of EAAT 2 mRNA. A schematic representation of the probe, thewild-type mRNA, and the aberrantly spliced mRNA (tr-2) are shown on theright.

FIG. 17A-17C are graphs showing that aberrant EAAT 2 mRNA speciescorrelate with the loss of EAAT 2 protein.

FIG. 18A is a diagram showing glutamate uptake related to varioustransfection paradigms using cDNA for the intron 7-retention mRNA. Thediagram includes representations of a Southern blot and a Western blotof expressed EAAT 2 mRNA and protein, respectively.

FIG. 18B is a diagram showing glutamate uptake related to varioustransfection paradigms using cDNA for the intron 7-retention mRNA. Thediagram includes a representation of a Western blot showing expressedEAAT 2 protein.

FIG. 19A is a representation of an immunoblot of COS7 cells expressingEAAT 2-GFP fusion protein using anti-GFP antibody.

FIGS. 19B-19I are fluorescence photomicrographs showing expression ofnormal and aberrant EAAT 2 fused with green-fluorescent protein (GFP) inCOS7 cells. Magnification=400×.

FIG. 20 is a drawing showing 5′-untranslated nucleotides from the normalhuman glutamate transporter 2 gene (SEQ ID NO: 60). The reportedtranscription start site is indicated.

DETAILED DESCRIPTION OF THE INVENTION

As summarized above, the present invention provides highly usefulmethods for detecting at least one specified neurological disorder in apatient. Further provided are novel polynucleotides that can be used inthe methods. Further provided are methods for isolating a variety ofaberrant human glutamate transporter 2 nucleic acids. Additionallyprovided are screening methods for detecting compounds that can boostnormal EAAT 2 polypeptide activity. Additionally provided arehybridization chips that can be used to facilitate detection of theneurological disorder.

In general, optimal practice of the present invention can be achieved byuse of recognized manipulations. For example, techniques for isolatingmRNA, methods for making and screening cDNA libraries, purifying andanalyzing nucleic acids, methods for making recombinant vector DNA,cleaving DNA with restriction enzymes, ligating DNA, introducing DNAinto host cells by stable or transient means, culturing the host cells,methods for isolating and purifying polypeptides and making antibodiesare generally known in the field. See generally Sambrook et al.,Molecular Cloning (2d ed. 1989), and Ausubel et al., Current Protocolsin Molecular Biology, (1989) John Wiley & Sons, New York.

As discussed above, the invention features methods for detecting atleast one type of aberrant EAAT 2 mRNA in a patient which methods areindicative of at least one specified neurological disorder in thepatient. As also discussed, the aberrant EAAT 2 mRNAs of this inventionfell into two broad classes: intron-retention EAAT 2 mRNA or an exonskipping EAAT 2 mRNA. Illustrative of each type of mRNA, shown at thelevel of cDNA, is provided in the drawings and examples, which follow.See e.g., FIGS. 2A-B and 3-11.

In particular, an intron-retention EAAT 2 mRNA of this invention willinclude a normal (i.e., full-length) or modified EAAT 2 mRNA fused to atleast a fragment of an EAAT 2 gene intron. In one embodiment, theintron-retention EAAT 2 mRNA includes a modified EAAT 2 mRNA fused tosubstantially all of the EAAT 2 gene intron or more than one intron upto about 2 or 3 of such introns. For example, the intron-retention EAAT2 mRNA can include a modified EAAT 2 mRNA fused to about 1%, 2%, 5%,10%, 20%, 30%, 50%, 60%, or 70%, up to about 80% or more of an EAAT 2gene intron. In another example, the intron-retention EAAT 2 mRNAincludes a modified EAAT 2 mRNA fused to substantially all of an EAAT 2gene intron up to 100% of that intron.

As is known in this field, the normal EAAT 2 gene generally includeintrons between exons 1 and 2, exons 2 and 3, exons 3 and 4, exons 4 and5, exons 5 and 6, exons and 7, exons 7 and 8, exons 8 and 9, exons 9 and10; and exons 10 and 11 of the normal EAAT 2 gene. Introns can beisolated by several techniques known in the field, e.g., hybridizationtechniques that detect repetitive intron sequences. The intronsgenerally have a nucleotide length of between about 500 to about 5000basepairs or more. An exemplary EAAT 2 gene intron is the intron betweenexons 7 and 8 of the EAAT 2 gene sequence (sometimes referred as intron7). A preferred intron-retention EAAT 2 mRNA includes between about 1 toabout 1000 and preferably about 1008 nucleotides of the intron 7sequence. See FIG. 13A and 13B below.

Reference herein to a “normal” EAAT 2 gene or related term is meant awild-type EAAT 2 gene sequence (including normal allelic variants) thatcan be found in healthy donors with no apparent nervous systemdysfunction. See, e.g., U.S. Pat. No. 5,658,782 which discloses thehuman EAAT 2 cDNA sequence, the disclosure of the which is specificallyincorporated herein by reference. See also FIGS. 1A-C and SEQ ID No. 1for the sequence of the cDNA complement of normal EAAT 2 mRNA sequence.

By the term “modified EAAT 2 mRNA” is meant an EAAT 2 RNA sequence(sometimes referenced as a primary EAAT 2 transcript) which RNA sequencehas been processed so that the processed RNA molecule lacks, eitherpartially or fully, exon sequence found in the full-length EAAT 2 mRNA.Such processing is often referred to as RNA “splicing”. For example, amodified EAAT 2 mRNA may lack at least about 2% to about 5%, at leastabout 10%, 20%, 30%, to 40%, 50%, 60% to about 80%, about 90% or about95% or more of the exon sequence found in the normal EAAT 2 mRNAsequence.

It will be apparent from the preceding discussion that some modifiedEAAT 2 mRNAs will be exon skipping EAAT 2 mRNAs. By the term “exonskipping” is meant specifically incorrect RNA processing of the primaryEAAT 2 RNA. That processing results in a modified EAAT 2 miRNA andparticularly an exon-skipping EAAT 2 mRNA. For example, the exonskipping EAAT 2 mRNA may lack, either partially or fully, sequenceencoded by at least one exon when compared to the full-length EAAT 2mRNA. In particular, the exon skipping EAAT 2 mRNA may lack all or partof sequence encoded by exons 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11 of theEAAT 2 gene. The exon skipping EAAT 2 mRNA may lack all or part ofsequence encoded by multiple exons, i.e. exons 2, 3, 4, 5, 6, 7, 8, 9,or 10. In some embodiments, the lack of sequence encoded by multipleexons may relate to a lack of contiguous or non-contiguous exons withrespect to exon organization of the EAAT 2 gene. Illustrative of suchexon skipping EAAT 2 mRNAs, shown at the cDNA level, are set forth belowand in the drawings. See FIG. 13A for an exon map of the normal EAAT 2cDNA.

By lack of at least part of an EAAT 2 exon is meant at least about 2%,5%, 10%, 20%, 40%, or 50%, preferably at least about 70%, 80%, 90%, andmore preferably at least about 95% up to 100% of the exon. See FIG. 13A,13B, and FIG. 12 for information relating to exon structure in the EAAT2 gene.

As noted, neurological disorders of specific interest include thoseassociated with abnormal release or removal of excitotoxic amino acidssuch as glutamate. Several CNS neuron types are especially adverselyaffected by excitotoxic glutamate. See e.g., Choi, D. W. (1988) Neuron1: 623; and references cited therein. Specifically preferredneurological disorders include AD, HD, PD with ALS being especiallypreferred.

As noted, preferred use of the present invention involves detecting atleast one specified neurological disorder in a subject, preferably amammal, and more preferably a human patient. That patient may have ormay be suspected of having (including having sometime in the future) theneurological disorder. Optimal practice of the invention generallyrequires obtaining a suitable biological sample. Preferred samples areobtained from a human patient although other samples can be obtained ifneeded. In particular, the biological sample can be obtained from asuitable cell line, tissue culture, or other source such as a tissue ororgan which is known to contain detectable amounts of RNA, preferablymRNA and more preferably EAAT 2 mRNA (normal and/or aberrant). Somebiological sources will include functional EAAT 2 polypeptide, e.g., aswhen the sample is obtained from an apparently healthy and non-affecteddonor. Methods for ascertaining apparently healthy and non-affecteddonors are known in the field.

Methods for detecting the EAAT 2 RNA or EAAT 2 polypeptide are known andinclude Northern blotting, Western blotting, and glutamate transportassays such as those specifically provided below. A preferred biologicalsample can be tissue obtained from the CNS, e.g., a biopsy taken fromthe brain. Preferred are those brain regions that are known to expressEAAT 2 polypeptide as provided below. Additional biological samples canbe obtained from fetal tissue if desired. Especially preferredbiological samples include nervous system fluid and especiallycerebrospinal fluid (CSF).

Reference herein to a “first biological sample” as typically obtainedfrom a control subject is meant to describe a sample from an apparentlyhealthy donor or other source that is known not to exhibit a specifiedneurological disorder. More specifically, the first sample will notinclude detectable levels of any aberrant EAAT 2 mRNA. Thus, the levelof normal EAAT 2 mRNA and/or EAAT 2 polypeptide in selected firstsamples provides a useful baseline from which to make variouscomparisons. As will be filly appreciated, once levels of the normalEAAT 2 mRNA and/or polypeptide are established for any healthy donor orgroup of donors, it is usually not necessary to assay for the normalEAAT 2 mRNA and polypeptide for each assay. As noted, preferred sampleswill typically include detectable RNA, preferably mRNA and particularlyEAAT 2 mRNA (normal and/or aberrant). By “detectable” is meant that thenucleic acid can be detected by any of the PCR methods, includingpreferred RT-PCR methods described herein.

Total cell RNA in a biological sample including mRNA can be purified foramplification by any of several methods if desired. Normal or aberrantEAAT 2 mRNA levels can be assayed using nearly any appropriate methodknown in the field including Northern analysis, single-stand nucleasemapping, particularly S1 nuclease mapping, PCR, reverse transcription incombination with PCR (RT-PCR), cloning, and reverse transcription incombination with a ligase chain reaction (RT-LCR). Additional methodsinclude use of commercially available kits for isolating and purifyingmRNA. See e.g., Chomczynski and Sacchi, Anal. Biochem. (1987) 162: 156for one method of isolating RNA.

As noted, it is generally preferred to detect normal and aberrant EAAT 2mRNA in a sample by amplification, preferably by PCR or a relatedmethod, more preferably by RT-PCR. Using RT-PCR, levels of intact andfull-length EAAT 2 mRNA can be readily measured, as can levels of anyaberrant EAAT 2 mRNAs present in the sample. See e.g., Makino et al.(1990) Technique 2: 295; Polymerase Chain Reaction (PCR): The Techniqueand Its Applications (1993) R.G. Landes Company for specific disclosurerelating to the methods. See also the specific examples provided below.

The RT-PCR can be performed by one or a combination of differentstrategies. For example, one method involves adding RNA from a suitablebiological fluid such as CSF in a reaction mixture including at leastone oligonucleotide primer, typically referred to as an RT primer, and asuitable buffer. In some cases, it may be useful to add an aliquot ofthe CSF directly to the reaction mixture. After allowing a sufficienttime for hybridization (annealing) of the RT primer to the RNA, thereaction can be supplemented with additional RT buffer, deoxynucleotidetriphosphates (dNTPs), DTT, one or more RNAse inhibitors such as RNAsin,and an appropriate amount of reverse transcriptase. After incubation fora sufficient time to allow reverse transcription of the RNA, the RTproducts and then subjected to PCR using suitable oligonucleotideprimers, e.g., a pair of such primers. The PCR primers can bedetectably-labeled if desired or a detectable label can be added to thePCR reaction to follow the amplification of the reverse transcriptiontemplate.

Methods for detectably-labeling nucleic acids are well known in thefield and include use of certain radionuclides, stable radioisotopes,chromophores, fluorophores and the like.

The PCR amplification can be achieved by a variety of suitable methodsincluding performing the reaction in a commercially available DNAthermal cycle. After a suitable number of rounds of amplification, theamplified PCR products, usually cDNA, are separated by molecular weighton an appropriate gel made, e.g., from polyacrylamide or agarose. Ifdesired, the amounts of the amplification products can be measured bydetecting the detectable label incorporated into the amplificationproducts. In most cases, use of a commercially available imaginganalyzer will be preferred. Various acceptable RT and PCR conditions andreagents are well known in the field. Specific RT-PCR reactionconditions are provided in the examples which follow. See e.g., Ausubelet al. supra; and Makino et al. supra.

Almost any pair of oligonucleotide primers that are capable ofamplifying the EAAT 2 gene sequence (exons, introns, or exons andintrons) are potentially useful for the purposes of this invention.Generally, a suitable oligonucleotide primer will be a DNA sequence ofbetween about 12 to about 70 nucleotides in length preferably about 20,30, 40, to about 50 or about 55 nucleotides in length. Theoligonucleotide primers can suitably include restriction sites to addspecific restriction enzyme cleavage sites to the PCR product as needed,e.g., to introduce a ligation site. Preferred DNA oligonucleotideprimers are spaced from one another in opposing direction relative toextension of the primers. That is, the primers are spaced relative toeach other on a polynucleotide template (usually on different strands)sufficient to produce an amplification product of at least about 50nucleotides, at least about 60 to about 100 nucleotides, at least about200 to 500 nucleotides, at least about 600 to 1000 nucleotides, or atleast about 1000 to 2500 nucleotides as determined, e.g., by gelelectrophoresis. Exemplary primers are provided in the examples andDrawings which follow.

Preferred methods of the invention include determining the DNA sequenceof PCR amplified products which products will preferably include DNAsequence, typically cDNA sequence, which is preferably substantiallyhomologous or identical to any one of the DNA sequences shown in SEQ IDNOS 3 & 5-13, respectively, in order of appearance (or the complementthereof).

By the term “substantially homologous” is meant relationship between twonucleic acid molecules and generally refers to subunit sequencesimilarity between the two molecules. Typically, the two nucleic acidmolecules will be DNA. When a subunit position in both of the DNAmolecules is occupied by the same monomeric subunit, i.e. a nucleotide,then they are homologous at that position. Homology between the twosequences is a direct function of the number of matching or homologouspositions, egg., if 50% of the subunit positions in the two DNAsequences are homologous then the two sequences are 50% homologous. By“substantially homologous” is meant largely but not wholly homologous.More particularly, the term is meant to denote at least about 60%, 70%,80%, 90%, 95% or greater homology up to about 99% homology with respectto any one of the DNA sequences illustrated in SEQ ID NOS 3 & 5-13,respectively, in order of appearance.

Two substantially homologous polynucleotides can be identified by one ora combination of different strategies. For example, in one approach, apolynucleotide of this invention that is substantially homologous to anyone of the DNA sequences shown in SEQ ID NOS 3 & 5-13, respectively, inorder of appearance (inclusive), in addition to fragments andderivatives thereof of a length sufficient to bind to the DNA sequencesin SEQ ID NOS 3 & 5-13, respectively, in order of appearance(inclusive), can be identified by employing moderately stringentconditions (referred to herein as “normal stringency” conditions). Inparticular, normal stringency conditions are meant to include ahybridization buffer comprising 20% formamide in 0.8M saline/0.08Msodium citrate (SSC) buffer at a temperature of 37° C. and remainingbound when subject to washing once with that SSC buffer at 37° C. Seee.g., Sambrook et al. supra. Additional methods include use ofcommercially available computer programs that can readily determinehomology between nucleic acids of known or partially known sequence.

Nucleic acid fragments and derivatives of this invention preferablyshould comprise at least about 20 to about 50 nucleotides, at leastabout 60, 100 to 200 nucleotides, at least about 300, 400, to about 500nucleotides, or at least about 1000, 1500, 2000 to about 2500nucleotides. In some preferred embodiments, the nucleic acid fragment orderivative is bound to some moiety, which permits ready identificationsuch as a radionucleotide, fluorescent or other chemical identifier.

As discussed, the invention provides methods for detecting at least onespecified neurological disorder in a subject. For example, in oneembodiment, the method includes obtaining a first biological sample froma control subject and a second biological sample from the patient,wherein the first and second samples each preferably comprise detectablemRNA. The method also includes contacting the first and second samplesindependently with at least two suitable oligonucleotide primers inwhich at least one primer, typically one of the primers, is capable ofhybridizing to the DNA sequence shown in SEQ ID NO. 1, e.g., undernormal stringency conditions. At least one other primer is capable ofhybridizing to an EAAT 2 intron sequence under the same or relatedstringency conditions. It is generally preferred that the contacting beconducted under conditions capable of hybridizing each primer pair tothe mRNA. The method further includes incubating any hybridized pair ofoligonucleotide primers in the first and second samples under conditionscapable of producing cDNA; and detecting in the second sample, any cDNAof between from about 25, 50, 100, 200, 300, 500, 600, 700, 900, 1000,1500 to about 2200 or about 2500 nucleotides in length as beingindicative of the neurological disorder in the patient.

The term “indicative of a neurological disorder” is used herein to meanthat presence of at least one type of EAAT 2 mRNA is taken to becorrelative with presence or risk of the disorder.

In preferred embodiments of the method, the neurological disorder isALS, HD, PD or AD, and most preferably ALS. Particularly preferred iswhen at least one of the oligonucleotide primers is capable ofhybridizing to the EAAT 2 gene intron 7 sequence under the normalhybridization conditions. Preferred primers are those capable ofproducing amplification products within the size ranges discussed above.Illustrative, are specific primers such as primer A (SEQ ID NO: 14) andprimer B (SEQ ID NO: 15). See the examples and drawings below.Alternatively, suitable oligonucleotide primers can be substantiallyhomologous to the primer A and/or primer B sequences.

Additionally provided is a method for detecting a neurological disorderin a subject such as a human patient in which the method includesobtaining a first biological sample from a control subject and a secondbiological sample from the patient in which each sample comprises mRNA.In one embodiment, the method includes contacting the first and secondsamples independently with at least a pair of oligonucleotide primersthat are capable of hybridizing to the DNA sequence shown in SEQ IDNo. 1. Typically, the contacting will be under conditions sufficient tohybridize the primers to the mRNA, such as the normal hybridizationconditions described above. In a particular embodiment, the methodincludes extending the pair of oligonucleotide primers in each of thefirst and second samples under conditions sufficient to produce cDNA;and detecting in the second sample any cDNA having a smaller nucleotidelength than cDNA in the first sample as being indicative of ALS in thepatient. The nucleotide size differential, if present, can be readilydetected by electrophoresis including polyacrylamide or agarose gelelectrophoresis using appropriate molecular weight markers (e.g., a HindIII digest of bacteriophage λ).

In this embodiment of the method, it is preferred that the neurologicaldisorder to be detected be ALS, HD, PD or AD, with ALS beingparticularly preferred. Additionally preferred are oligonucleotideprimers which are capable of hybridizing to the normal EAAT 2 cDNAsequence set forth in SEQ ID No. 1, e.g., under normal or relatedhybridization conditions. Preferred primers are those capable ofproducing amplification products within the size ranges discussed above.Illustrative are primer A (SEQ ID NO: 14) and primer C (SEQ ID NO: 16)as set forth in the examples below. Alternatively, suitableoligonucleotide primers can be substantially homologous to the primer Aand/or primer C sequences.

The term ” complementary” or like term refers to the hybridization orbase pairing between nucleotides or nucleic acids, such as, forinstance, between the two strands of a double stranded DNA molecule orbetween an oligonucleotide primer and a primer binding site on a singlestranded nucleic acid to be sequenced or amplified. Complementarynucleotides are, generally, A and T (or A and U), or C and G. Two singlestranded RNA or DNA molecules are said to be substantially complementarywhen the nucleotides of one strand, optimally aligned and compared andwith appropriate nucleotide insertions or deletions, pair with at leastabout 95% of the nucleotides of the other strand, usually at least about98%, and more preferably from about 99 to about 100%. Complementarypolynucleotide sequences can be identified by a variety of approachesincluding use of well-known computer algorithms and software.

The present invention also features methods for detecting a neurologicaldisorder in a subject such as a human patient which method involvesisolating mRNA from a biological sample and contacting the mRNA in thesample with a nucleic acid comprising a polynucleotide sequence,preferably a DNA sequence, that is complementary to an intron or intronfragment from the normal EAAT 2 gene. The contacting will generally beunder hybridization conditions capable of forming a specific bindingcomplex between the mRNA and the nucleic acid. The method furtherincludes detecting the binding complex as being indicative of theaberrant human glutamate transporter 2 (EAAT 2) mRNA in the sample.

In one embodiment, the method specifically includes treating the bindingcomplex with a single-strand nuclease particularly SI nuclease andidentifying any hydrolyzed nucleic acid as being indicative of theaberrant human glutamate transporter 2 (EAAT 2) mRNA in the sample. In aparticular embodiment, the intron sequence is from intron 7 of the EAAT2 gene. See the examples, which follow for specific disclosure relatingto use of S1 nuclease. See also Ausubel et al. supra; and Sambrook etal. supra.

By the term “specific binding” or similar term is meant a moleculedisclosed herein which binds another molecule, thereby forming aspecific binding pair, but which does not recognize and bind to othermolecules as determined by, e.g., Western blotting, Northern or Southernblotting, ELISA, RIA, gel mobility shift assay, enzyme immunoassay,competitive assays, saturation assays or other suitable protein bindingassays known in the field.

Further provided is a method of isolating an aberrant EAAT 2 cDNA. Inone embodiment, the method includes obtaining a first biological samplefrom a control subject and a second biological sample from a patient inwhich the method includes producing cDNA in each of the first and secondsamples. In this embodiment, the cDNA comprises DNA sequencesubstantially homologous to SEQ ID NO. 1 and then introducing the cDNAfrom the first sample into control cells under conditions sufficient toexpress the cDNA in the control cells. Typically, introduction of thecDNA from the first sample and the second sample into test cells isperformed under conditions sufficient to express the cDNA in the testcells. The method also includes detecting a reduction in glutamatetransport in the test cells compared to the control cells as indicativeof isolation of the aberrant human glutamate transporter 2 (EAAT 2)cDNA.

Additional methods for isolating the aberrant EAAT 2 cDNA includehybridization of cDNA libraries made from the sample withdetectably-labeled probes to detect homologous or substantiallyhomologous sequences.

The term “standard glutamate assay” or like term is meant to include oneor more of the following steps:

-   -   a) making a first recombinant vector comprising DNA sequence        encoding the normal EAAT 2 cDNA (SEQ ID NO. 1) or a suitable        fragment thereof,    -   b) making a second recombinant vector comprising DNA sequence        encoding an aberrant EAAT 2 cDNA of interest, e.g., the cDNA        sequence illustrated in SEQ ID NO: 3,    -   c) introducing the first vector into a suitable cells such as        COS-7 cells (control cells),    -   d) introducing the second vector into COS-7 cells or other        suitable cells (test cells);    -   e) adding detectably-labeled glutamate; and    -   f) detecting glutamate transport in the control cells and any        glutamate transport in the test cells.

As will be appreciated, the standard glutamate assay can be modified inseveral ways to suit intended use. For example, in instances where abaseline level of EAAT 2 gene or cDNA expression has been established inthe control cells, it may not always be necessary to make the firstrecombinant vector or to introduce same into the control cells. In thisembodiment, results from the test cells can be directly compared to thebaseline level if desired.

Typically, the standard glutamate assay is a sodium-dependent glutamatetransport assay. Introduction of the recombinant vectors in accord withthe standard glutamate assay can be conducted by any acceptable means,e.g., retroviral transfer, viral or bacteriophage infection, calcium-,liposome-, DEAE or polybrene-mediated transfection, biolistic transfer,or other techniques known in the art. See Sambrook, et al. supra;Ausubel, et al. supra.

In one embodiment of the standard glutamate essay, the test and controlcells are washed following introduction of the recombinant vectors andthen incubated with a suitable amount of detectably-labeled glutamate,e.g., ³H-labeled glutamate (DuPont-NEN) and non-labeled glutamate.Following a suitable incubation interval, test and control cells arewashed several times in a suitable wash buffer such as ice-cold PBS,solublized in a solution comprising about 0.1% SDS and the amount ofradioactivity associated with the cells determined using conventionalscintillation counting methods.

An especially preferred glutamate transport assay has been disclosed byRothstein et al. (1995) Ann. Neurol. 38: 78. See also Rothstein et al.(1992) N. Engl. J Med. 326: 1464. The disclosures of which arespecifically incorporated by reference. See also the examples anddrawings, which follow.

As noted, the present invention further provides polynucleotidesequences substantially homologous or identical to the DNA sequencesrepresented in SEQ ID NOS 3 & 5-13, respectively, in order of appearance(inclusive) or the complement thereof. A complementary sequence mayinclude an antisense polynucleotide which can be DNA, RNA, cDNA, cRNAgenomic DNA or chimeras thereof. When the sequence is RNA, thedeoyribonucleotides A, G, C, and T will be replaced by ribonucleotidesA, G, C and U, respectively. Also included in the invention arefragments or derivatives of such sequences.

The polynucleotide sequences of the invention can be altered bymutations such as substitutions, additions or deletions that can providefor substantially homologous nucleic acid sequences. In particular, agiven nucleotide sequence can be mutated in vitro or in vivo, to createvariations in the nucleotides, e.g., to form new or additionalrestriction endonuclease sites or to destroy preexisting ones andthereby to facilitate further in vitro modification. Any technique formutagenesis known in the art can be used including, but not limited to,in vitro site-directed mutagenesis (Hutchinson et al., J. Biol. Chem.,253:6551 (1978)), use of TAB Registered TM linkers (Pharmacia),PCR-directed mutagenesis, and the like.

The isolated nucleotide sequences of the invention may be cloned orsubcloned using any method known in the art. See e.g., Sambrook, J. etal., supra. In particular, nucleotide sequences of the invention may becloned into any of a large variety of vectors. Possible vectors include,but are not limited to, cosmids, plasmids or modified viruses, althoughthe vector system must be compatible with the host cell used. Viralvectors include, but are not limited to, lambda, simian virus, bovinepapillomavirus, Epstein-Barr virus, and vaccinia virus. Viral vectorsalso include retroviral vectors, such as Amphatrophic Murine Retrovirus(see Miller et al., Biotechniques, 7:980-990 (1984)), incorporatedherein by reference). Plasmids include, but are not limited to, pBR,pCMV5, PUC, pGEM (Promega), and Bluescript θ (Stratagene) plasmidderivatives. Introduction into and expression in host cells is done forexample by, transformation, transfection, infection, electroporation,etc. See the examples which follow for particularly preferredrecombinant vectors.

For preferred production of anti-sense RNA, use of specified recombinantvectors typically including strong bacterial or eukaryotic (e.g., viral)promoters will usually be desired. See e.g., Ausubel et al. supra andthe discussion which follows.

The term “vector” or “recombinant vector” as used herein means anynucleic acid sequence of interest capable of being incorporated into ahost cell and resulting in the expression of a nucleic acid sequence ofinterest. Vectors can include, e.g., linear nucleic acid sequences,plasmids, cosmids, phagemids, and extrachromosomal DNA. Specifically,the vector can be a recombinant DNA. Also used herein, the term“expression” or “gene expression”, is meant to refer to the productionof the protein product of the nucleic acid sequence of interest,including transcription of the DNA and translation of the RNAtranscript. Most recombinant vectors will include a “cloning site” whichas used herein is intended to encompass at least one restrictionendonuclease site. Typically, multiple different restrictionendonuclease sites (e.g., a polylinker) are contained within the vectorto facilitate cloning.

Exemplary host cells which can express the isolated nucleic acids ofthis invention include bacterial cells (e.g., E. coli) such as MM294,DM52, XL1-blue (Stratagene) strains of E. coli, and animal cells (e.g.,CV-1 and COS-7 cells). In addition, it is possible to express certainisolated nucleic acids of the invention in certain yeast cells (e.g., S.cerevisiae), amphibian cells (e.g., Xenopus oocyte), and insect cells(e.g., Spodoptera frugiperda and Trichoplusia ni). Methods forexpressing isolated and recombinant DNA in these cells are known. Seee.g., Sambrook et al., Molecular Cloning (2d ed. 1989), Ausubel et al.supra, and Summer and Smith, A Manual of Methods for Baculovirus Vectorsand Insect Cell Culture Procedures: Texas Agricultural ExperimentalStation Bulletin No. 1555, College Station Texas (1988).

A “polypeptide” refers to any polymer consisting essentially of any ofthe 20 amino acids regardless of its size. Although the term “protein”is often used in reference to relatively large proteins, and “peptide”is often used in reference to small polypeptides, use of these terms inthe field often overlaps. The term “polypeptide” refers generally toproteins, polypeptides, and peptides unless otherwise noted.

As will be described in more detail by the examples and discussion whichfollows, in most cases, aberrant EAAT 2 mRNA of this invention will giverise to negligible or undetectable levels of polypeptide. However, wheresignificant levels of polypeptide can be deleted, e.g., as when otherhost cells conducive to polypeptide production or stability are used,conventional immunological methods can be used to raise antibodies,preferably monoclonal antibodies, against the polypeptides. Thepolypeptides can be detected by a variety of means including westernblots using anti-EAAT 2 antibodies.

Additional antibodies of interest will be those directed againstspecified oligopeptide sequences. The oligopeptides will generally beamino acid sequence spanning a deletion site in an aberrant EAAT 2 mRNAsequence, i.e. the abnormal splice site. The oligopeptide sequences canbe make synthetically by techniques well known in the field. Methods formaking oligopeptide sequences and antibodies have been disclosed inAusubel et al. supra and Harlow and Lane in, Antibodies: A LaboratoryManual (1988).

A further embodiment of the present invention provides methods forscreening a biological sample for at least one specified neurologicaldisorder. More particularly, the method can be used as a diagnostic aidto screen the biological sample. Diagnostic aids and methods for usingthe diagnostic aids are particularly useful when it is desirable toscreen the biological sample for presence of a at least one aberrantEAAT 2 mRNA. Such an approach would be especially useful for thedetection of the aberrant EAAT 2 mRNAs in particular patients having orsuspected of having at least one specified neurological disorder.Additionally useful is detection among families of patients, e.g., toanalyze incidence of phenotypic, genetypic (allelic), or somatic EAAT 2gene variation.

In a particular embodiment, the diagnostic aids include specificpolynucleotides of this invention that have been fixed (i.e. preferablycovalently attached) to a solid support which support is typicallycontacted with the biological sample (or more than one of such samples).The polynucleotide can be fixed directly to the support or indirectlythrough a suitable linker as needed. Detection of hybridization (ifpresent) between at least one target nucleic acid in the sample and atleast one fixed polynucleotide on the support is taken to be indicativeof at least one neurological disorder in the patient from which thesample was obtained. It will be appreciated that in many cases thetarget nucleic acid will be RNA and particularly mRNA although in somecases the target can be cDNA.

In most cases, the specified polynucleotides will be DNA typically of alength of between at least about 5 nucleotides to about 20 nucleotides,preferably at least about 10 to about 25 to about 30 nucleotides inlength. However, certain sold supports are known to be compatible withlarger DNA molecules, e.g., at least about 35 nucleotides, up to about40, 45, 50, 60, up to about 100 nucleotides, at least about 200nucleotides up to about 300, 400, 500, 600, 700, up to about 1000, 2000to about 2500 nucleotides or more if desired. The polynucleotides can besuitably single- or double-stranded according to intended use. Thepolynucleotides can be made by any acceptable means including synthetic,recombinant, or semi-synthetic approaches known in the field.

In one embodiment, the specified polynucleotide is single-stranded DNAthat is complementary to sequence of an aberrant EAAT 2 mRNA whichsequence is not present in the normal EAAT 2 mRNA. For example, in oneembodiment, the diagnostic aid can include a single-stranded DNA boundto a suitable solid support in which the DNA consists of intronicsequence from the EAAT 2 gene. In a particular embodiment, thesingle-stranded DNA consists of sequence from intron 7. Illustrations ofsuch a DNA molecule is primer B (SEQ ID NO: 15). In another embodiment,the single-stranded DNA includes sequence complementary to a novel RNAsplice site sequence that is present in the EAAT 2 mRNA but not thenormal EAAT 2 mRNA. The examples and drawings which follow provideillustrative RNA splice site sequences, shown at the level of cDNA, thatcan be used to make suitable single-stranded DNA oligonucleotides. Seee.g. FIGS. 2A-B, 3-11, 13A and 13B.

In another embodiment, the specified polynucleotide is a DNA sequencesubstantially homologous to any one of the sequences shown in FIGS.2A-B, 3-11, 13A and 13B. (SEQ ID NOS 3 & 5-13, respectively in order ofappearance (inclusive)).

As noted, the diagnostic aid includes a solid support that is capable ofcovalently binding directly and indirectly a specific polynucleotidewhich can be a suitable single-stranded nucleic acid as described above.Preferred are solid supports including or consisting of a plastic,ceramic, metal, resin, gel, or a membrane. A more preferred exampleincludes a two-dimensional, or three-dimensional matrix, such as a gel,with potential multiple binding sites for the specified polynucleotide.Thus, in one embodiment, the solid support includes a plurality of asingle type of bound polynucleotide as described. In this embodiment,the solid support has capacity to recognize (i.e. hybridize) one type oftarget if present in the sample. In another embodiment, the solidsupport includes at least two types of bound polynucleotide (e.g., (SEQID NOS 3 & 5-13, respectively, in order of appearance) differentpolynucleotides). In this specific embodiment, the solid support hascapacity to bind (SEQ ID NOS 3 & 5-13, respectively, in order ofappearance) different targets, respectively, in the sample.

An especially preferred solid support for binding at least one specifiedpolynucleotide of this invention is a hybridization chip. See e.g.,Pevzner et al. (1991) J. Biomol. Struc. & Dyn. 9: 399; Maskos andSouthern (1992) Nucl. Acids. Res. 20: 1679; Johnston, M (1998) CurrentBiology 8: R171; and U.S. Pat. Nos. 5,631,134 and 5,556,752 to Cantorand Lockhart et al., respectively, for methods of making and usinghybridization chips comprising a desired nucleic acid.

An illustrative hybridization chip uses at least one type of cDNAprinted on a glass surface so that the chip can provide a high-densityhybridization target. The chip can be contacted with adetectably-labeled mixture of mRNA obtained from a biological sample ofinterest. Detection schemes can be employed to provide rapid andsimultaneous expression analysis of independent biological samples. Seee.g., Schena M. Bioessays (1996) 18: 427; and Schena M. et al. (1995)Science 270: 467.

More particularly, hybridization chips can be used with one or more thanone type of polynucleotide of this invention. When the hybridizationchip is contacted with a desired biological sample any hybridizationtherein can be analyzed by one or a combination of different approaches.For example, the target nucleic acids can be detectably-labeled with anysuitable label as described herein including a radioisotope, a stableisotope, an enzyme, a fluorescent molecule, a luminescent molecule, achromophore, metal, electric charge, or a detectable structure such asan epitope. Methods for detectably labeling the target nucleic acids aregenerally known in the field. The label may be directly or indirectlydetected using scintillation counting, an imaging implementation, ormass spectrometry. Preferred methods of detection include use of wavedetection of surface plasmon resonance of thin metal film labels such asgold, by, e.g., BIAcore sensor (Pharmacia) or other suitable biosensors.

An especially preferred embodiment is a hybridization “micro-chip”comprising one or more than one specified polynucleotide of thisinvention. Such a chip will be particularly useful, e.g., in detectingat least one type of aberrant EAAT 2 mRNAs in CSF obtained from apatient. Hybridization, if present, can be detected by BIAcore or othersuitable method.

Further provided by the present invention are methods for screeningcompounds useful in the diagnosis or treatment of a neurologicaldisorder of interest, preferably ALS. In general, the compounds will becandidate compounds that will be selected for capacity to modulateexpression of the normal EAAT 2 gene in suitable host cells or tissueparticularly in the presence of at least one type of aberrant EAAT 2mRNA or cDNA. Preferred compounds will increase the expression by atleast about 10%, at least about 20% to about 30%, at least about 50% toabout 70%, at least about 80% to 95%, and at least about 100% or morewhen compared to a suitable control assay without addition of thecompound. In preferred embodiments, suitable cells such as Cos-7 cellsare co-transformed with a recombinant vector including a normal and anaberrant EAAT 2 cDNA. The transformed cells are then contacted with thecompound, and the effect of the compound, if any, on expression of thenormal cDNA is determined, e.g., by Northern hybridization or by thestandard glutamate transport assay discussed above. Of particularinterest are agonists of the normal EAAT 2 cDNA expression.

Further provided by the invention is a method of treating or preventinga neurological disorder in a patient, the method comprisingadministering a therapeutically effective amount of a suitablerecombinant vector capable of expressing an anti-sense nucleic acid,e.g., antisense RNA, which is capable of specifically binding at leastone type of aberrant EAAT 2 mRNA.

The recombinant vector can be administered to a patient in need oftreatment by one or a combination of strategies. For example, in oneembodiment, the method includes administering to the patient at leastone of the recombinant vectors in a form that permits entry of theconstruct into patient cell or groups of cells including tissues ororgans. Preferred cells are those in the nervous system such as neurons,glia, and astrocytes. The administration may be carried out by any ofvarious techniques known, for example, in the art of gene therapy. (seee.g., J. W. Larrick and Kathy L. Burck, (1991) Gene Therapy, Applicationof Molecular Biology, (Elsevier, Holland). In another embodiment, atleast one of the recombinant vectors is administered by use ofliposomes, e.g., immunoliposomes, according to techniques known in thefield. Use of immunoliposomes has several advantages including thecapacity to target contents to a desired cell or tissue type.Alternatively, the recombinant vector may be delivered via injection toa desired site including continuous injection via a shunt. Although notalways optimal, delivery by way of mucosally-lined passages; or via theairways, for example; may be useful in some instances. See e.g., U.S.Pat. No. 5,624,803 to Noonberg et al. and references cited therein forcompositions and methods for delivering of antisense oligonucleotidesinto desired cells.

Preferred in some instances is viral integration of at least one of therecombinant vectors into the chromosome of a desired cell. In thisembodiment, it is possible to confer permanence or semi-permanence toexpression of the recombinant vector in the cell or tissue of interest.

As noted, the invention can also be used to evaluate the efficacy of atherapy employed to treat a neurological disorder in a patient. In oneembodiment, the disorder is ALS. In this embodiment, treatment of theALS patient includes or consists of treatment with Rilutek™ (riluzole),a benzothiazole used to treat ALS. In this embodiment, an increase innormal EAAT 2 protein or mRNA in the patient will be taken as indicativeof a beneficial effect of the drug in the patient. Although nearly anyincrease in the levels of normal EAAT 2 protein or mRNA will beconsidered beneficial to the patient, an increase of normal EAAT 2protein or mRNA in the range of about 1.5 to about 10 fold or morerelative to a suitable control will be especially desirable. It will beappreciated that the increase observed will depend on several factors asthe age, sex and general health of the patient. A suitable control willinclude testing the patient prior to administration of the drug. Theincrease in normal EAAT 2 protein or mRNA can be evaluated by a varietyof methods including measuring the increase relative to incidence of atleast one type of aberrant EAAT 2 mRNA in the patient. It is preferredthat the method be performed on CSF although other biological samplescan be used if desired. The increase in normal EAAT 2 protein can bedetermined by assays disclosed herein (e.g., Western blots, Northernblots or PCR). Rilutek™ is available from Rhone-Poulenc RorerPharmaceuticals Inc. Collegeville, Pa. 19426-0107. See also thePhysicians' Desk Reference (1998) (Medical Economics Company, Inc.,Montvale, N.J.) pages 2380-2883 for therapies employing Rilutek™.

As noted, the invention also provides a kit for detecting at least onespecified neurological disorder in a patient. In a preferred embodiment,the kit includes at least one container means. The container meansincludes a system for detecting the neurological disorder in thepatient, wherein the system comprises at least one of: 1) at least apair of oligonucleotide primers capable of specifically binding to anyone of the DNA sequences of SEQ ID NOS 3 & 5-13, respectively, in orderof appearance or the complement thereof; 2) an antibody capable ofspecifically binding a polypeptide encoded by an aberrant humanglutamate 2 (EAAT 2) mRNA; 3) a hybridization chip comprising at leastone isolated nucleic acid substantially homologous or identical to anyone of the DNA sequences of SEQ ID NOS 3 & 5-13, respectively, in orderof appearance or the complement thereof; and 4) a polynucleotidesequence comprising sequence substantially homologous or identical toany of the DNA sequences of SEQ ID NOS 3 & 5-13, respectively, in orderof appearance (inclusive) or the complement thereof.

Additionally provided is a kit to treat a neurological disorder in thepatient, which kit includes at least one container means including arecombinant vector capable of producing an anti-sense nucleic acidsubstantially homologous or identical to any of the DNA sequences of SEQID NOS 3 & 5-13, respectively in order of appearance or the complementthereof. In one embodiment, the anti-sense nucleic acid is RNA.Components of the kit can be used alone or with other therapeuticcompounds as needed.

A kit of this invention may include additional components, as needed,including suitable buffers, indicators (e.g., fluorophores, chromophoresor enzymes providing same), controls (e.g., a suitable polynucleotide ofthis invention) and directions for using the kit. Kit components can beprovided in nearly any acceptable form, including a liquid or solid,e.g, as a lyophilized powder.

Further provided is cDNA library comprising sequence substantiallyhomologous to the DNA sequence of any one of SEQ ID NOS 3 & 5-13,respectively, in order of appearance or the complement thereof.

Polynucleotides of this invention are typically isolated, meaning thatthe polynucleotides usually constitute at least about 0.5%, preferablyat least about 2%, and more preferably at least about 5% by weight oftotal polynucleotide present in a given fraction. A partially purepolynucleotide constitutes at least about 10%, preferably at least about30%, and more preferably at least about 60% by weight of total nucleicacid present in a given fraction. A pure polynucleotide constitutes atleast about 80%, preferably at least about 90%, and more preferably atleast about 95% by weight of total polynucleotide present in a givenfraction. Purity can be determined by standard methods including gelelectrophoresis.

It is preferred that the polypeptides of the present invention besubstantially pure. That is, the polypeptides have been isolated fromcell substituents that naturally accompany it so that the polypeptidesare present preferably in at least 80% or 90% to 95% homogeneity (w/w).Polypeptides having at least 98 to 99% homogeneity (w/w) are mostpreferred for many pharmaceutical, clinical and research applications.Once substantially purified the polypeptide should be substantially freeof contaminants for therapeutic applications. Once purified partially orto substantial purity, the polypeptides can be used therapeutically, orin performing a desired assay. Substantial purity can be determined by avariety of standard techniques such as chromatography and gelelectrophoresis.

The following are non-limiting examples of the present invention.

EXAMPLE 1 Identification of Aberrant EAAT 2 Transcripts in ALS AffectedAreas

1.cDNA from Patient Motor Cortex

A male ALS patient (66 years old, 5 hr postmortem delay), without SOD1mutations, was initially investigated. This patient was chosen becauseimmunoblot studies revealed extremely low levels of EAAT 2 protein (5%of control) in motor cortex (Rothstein et al. (1995) Ann. Neurol. 38,73). The Northern blotting revealed that the quantity and size of EAAT 2mRNA were normal (Bristol, L. A., and Rothstein, J. D. (1996) Ann.Neurol. 39, 676). To investigate whether there were aberrant EAAT 2 mRNAspecies, a cDNA library was constructed from a poly (A)⁺ mRNA preparedfrom the motor cortex of this patient. The cDNA library was thenscreened and an abnormal cDNA clone was subsequently identified frompositive clones by restriction analysis. Sequencing of this clonerevealed that it contained 1091 bp of the EAAT 2 coding region from exonI to exon 7, followed by 1008 bp of intron region, corresponding topartial sequence of intron 7, ending with a poly A tail (Aoki et al.(1998) Ann. Neurol. 43, In press) (FIG. 13A). A stop codon was foundimmediately after this exon and intron junction. Thus, the presumedtranslation product would be EAAT 2 protein truncated after codon 364.

FIG. 13A is a schematic presentation of abnormally processed partialintron 7-retention and exon 9-skipping species in relation to the normalEAAT 2 gene. Probe E corresponds to position 1687 to 2210 from the 5′translation region. Probe F corresponds to position 537 to 1008 fromexon 7 intron junction.

To ensure that it was not a cloning artifact, reverse-transcriptionpolymerase chain reaction (RT-PCR) with the use of a primer pair thatincluded normal exon and intronic sequences (FIG. 13A, primer A and B),was performed on equal amounts of poly (A)⁺ mRNA (DNase I treated)prepared from motor cortex of the ALS patient and normal controls. Asshown in FIG. 14A (at intron-retention EAAT 2; ALS patient 3), a strongsignal was observed in the ALS specimen, but not in the controlspecimens.

FIG. 14A shows analysis of EAAT 2 protein (Western blot) and aberrantEAAT 2 mRNA species (RT-PCR/Southern blot) in ALS and control motorcortex. Aliquots of tissue homogenates from control or ALS motor cortexwere subjected to SDS-polyacrylamide gel electrophoresis andimmunoblotted with affinity-purified polyclonal carboxy-terminalantibody to EAAT 2. Controls included non-neurological andneurodegenerative disease specimens. Individual lanes are numbered foreach patient. RT-PCR was performed on parallel tissue samples from eachcontrol or ALS motor cortex specimen. An internal control was designedfor comparative analysis of the partial intron 7-retention mRNA betweensamples.

2. cDNA from Spinal Cord and Motor Cortex (Patient and Control)

As another approach, RT-PCR was used to amplify EAAT 2 cDNA fragmentsfrom poly (A)⁺ mRNA prepared from the spinal cord or motor cortex of thepatient and from normal controls. A shorter PCR fragment wassubsequently identified, using primer A and C (FIG. 13A), which wasamplified along with the normal size PCR fragment in the patient, butwas not present in normal controls (FIG. 14A; at exon 9-skipping EAAT 2,ALS patient 2). The shorter PCR fragment was cloned. DNA sequencingrevealed it to be a 135 bp in-frame deletion in which exon 8 is linkeddirectly to exon 10, demonstrating that it arises from skipping of exon9 (Aoki et al., 1998 supra) (FIG. 13A).

Furthermore, when primers D and C (FIG. 13A) were used to amplify thefull length EAAT 2 coding region, a large amount of shorter PCRfragments were observed in motor cortex of ALS, but not in normalcontrols (FIG. 14C). All the shorter PCR fragments from ALS patient #3(FIG. 14C) were then cloned. Twenty clones were randomly selected andanalyzed by restriction digestion. All of the these clones were found tohave different internal deletions. In addition, a single band from thegel (Patient 3, FIG. 14C) was cloned and was found to consist ofmultiple internally deleted cDNA, all similar in size. These resultsindicate that there are many different truncated EAAT 2 transcripts inALS motor cortex.

Eight of the truncated cDNAs were then sequenced at the junction of thedeletion regions (FIG. 13B). Two cDNAs were found to be truncated due toexon-skipping (FIGS. 13B ₇ and 13B₈ ). One cDNA was truncated at theappropriate splicing donor and acceptor sites (FIG. 13B ₅). Othertruncated cDNAs were identified, although the deletions did not occur atcommon splicing sites (FIG. 13B ₁₋₄, 13B₆). The presence of multipleprecise exon-skipping deletions (FIG. 13A and 13B) suggest that it isvery unlikely that they could be caused by somatic DNA deletions. Theabundance of multiple truncated transcripts may be the result ofaberrant RNA splicing.

3. Defect Specificity by Brain Region and Transporter Subtype

To examine the specificity of these defects for brain region andtransporter subtypes, ALS and control tissue from several brain regionsin the same patient was examined. As shown in FIG. 14C, multipletruncated EAAT 2 mRNAs were found in ALS motor cortex, but notcerebellum or hippocampus from the same patient (3). Similar resultswere obtained every ALS patient examined (n=20). Other cell specific andgeneral cellular mRNA species were examined. Truncated transcripts werenot found for the astroglial glutamate transporter EAAT1 (FIG. 14D), theneuronal protein EAAT3, or the constitutive spliceosomal assemblyprotein, survival motor neuron (SMN) (Fischer et al. (1997) Cell 90,1023; Liu et al. (1997). Cell 90, 1013). (FIG. 14D). EAAT1 and EAAT3protein levels were previously shown to be normal in ALS (Rothstein etal., 1995 supra).

Thus, the results indicate that these aberrant RNA species were specificfor ALS and were not an artifact. They were not observed in a smallsample of other neurodegenerative disorders—Huntington's disease,Alzheimer's disease, and spinal muscular atrophy; they were found onlyin ALS neuropathologically affected brain regions, while unaffectedbrain regions in the same patients had normal EAAT 2 RNA; othertransporter proteins, and constitutive RNA species were not affected.See Example 9 below.

3. Tissue and Cerebrospinal Fluid Specimens

ALS brain and spinal cord tissue was obtained from the Johns Hopkins ALSBrain Bank and the Alzheimer's Disease Research Center Brain Bank, withinstitution-approved informed consent. Post-mortem delays for autopsywere generally less than 12 hr. ALS and some control tissue was rapidlydissected; dissected regions were rapidly frozen (isopentane/dry ice),and then stored at −75° C. until use. Additional specimens were fixed in4% paraformaldehyde. Pathological confirmation of ALS was made on allspecimens by standard histological evaluation of spinal cord and motorcortex, with use of hematoxylin and eosin to evaluate motor neuron loss,and with myelin stains (Luxol-fast blue) to establish corticospinaltract degeneration. SOD1 mutation analysis was performed. Pathologicallyconfirmed Alzheimer's disease and Huntington's disease brain tissue wasprovided by the Johns Hopkins Alzheimer's Disease Research Center BrainBank. SMA spinal tissue was obtained at autopsy from patients diagnosed.Cerebrospinal fluid was obtained at the time of diagnostic evaluationfor ALS and control patients with institution-approved informed consent.CSF was rapidly frozen and stored at −20 to −70° C. for up to 6 years.

The clinical diagnosis of ALS was made by the El Escorial criteria(Brooks, (1994) J. Neurol. Sci. 124 (suppl.) 96. including the presenceof both upper and lower motor neuron signs, a definite history ofprogression, absence of sensory abnormalities, normal nerve conductionvelocities and late responses, and electromyographic evidence of diffuseenervation. Patients typically were initially classified as havingeither probable or definite ALS based on these criteria. Patients wereexcluded if they had unexplained bowel or bladder changes, anatomic,metabolic, or toxic disorders that could mimic ALS, e.g. endocrineabnormalities, hexosaminidase A deficiency, lead intoxication,myelopathy, or peripheral neuropathy.

4. Methods

Poly (A) mRNA was isolated by using the FastTrack 2.0 mRNA isolation kit(Invitrogen). cDNA was synthesized from the isolated mRNA by using ZAPexpress cDNA synthesis kit (Stratagene). The cDNA was size-fractionatedinto three fractions, >6 kb, 3-6 kb, and <3 kb, by Sephacryl S-500 spincolumn. Each cDNA fraction was ligated into the ZAP express vector armsand packaged into Gigapack III Gold packing extract (Stratagene). ThecDNA library was subsequently screened by a DNA probe prepared from fulllength EAAT 2 cDNA by random priming. The positive clones in the pBK-CMVphagemid were obtained after in vivo excision from the ZAP expressvector with ExAssist helper phage.

Poly (A) mRNA was isolated from 50-100 mg of specimens (motor cortex,frontal cortex, hippocampus, caudate, cerebellum, lumbar or cervicalspinal cord) by using Micro-Fast Track Kit (Invitrogen). The isolatedmRNA was treated with DNase I for 20 min, heated to 65° C. for 5 min,and then reverse transcribed into cDNA. A 25 μl reverse transcriptionreaction mixture containing 50 mg of RNA, 1 mm dithiothreitol, 0.5 mMdNTPs, 20 units of RNasin, 200 units of M-MLV reverse transcriptase(BRL), 1× buffer, 0.5 μM primer (primer B for the intron-retention andprimer C for the exon 9-skipping and the full length cDNA) was incubatedat 42° C. for 60 min, heated to 65° C. for 5 min, and quick-chilled onice. PCR was performed at a final concentration of 1× PCR buffer/0.2 mMdNTPs/0.5 μM each 5′ and 3′ primers (primer A and B for theintron-retention; primer A and C for the exon 9-skipping; primer D and Cfor the full length; FIG. 13A, 13B)/2 units of Taq polymerase(Boehringer Mannheim)/2.5 μl of reverse transcription reaction mixturein a total volume of 50 μl. The mixture was overlaid with mineral oiland then amplified with the Delta cycler II thermal cycler (Ericonip)for 25 or 30 cycles. The amplification profile involved denaturation at94° C. for 30 sec, primer annealing at 55° C. for 30 sec, and extensionat 72° C. for 1 min. PCR products (10 μl) were resolved by 1.2% agarosegel electrophoresis and transferred to membrane. The blot was probedwith a ³²P-labeled EAAT 2 cDNA probe prepared by the random primingmethod (FIGS. 14A and 18A, 18B) or a ³²P-end labeled oligonucleotideprobe (FIGS. 14B, 14C, 16A and 16C) and then subjected toautoradiography. The same RT-PCR conditions were used to analyze EAAT1mRNA.

To screen for intron-retention mRNA, a plasmid (pE2F) was constructedfor use as an internal control for the comparative analysis of theintron-retention mRNA between patients. A 185 bp DNA fragment with HindIII on both ends was inserted into the intronic mutant cDNA at a HindIII site (indicated in FIG. 13A, triangle). This plasmid, pE2F, was usedas a template for transcription by the T3 polymerase. The resulting pE2Fcomplementary RNA (cRNA) product was purified by oligo (dT)chromatography. 50 mg of mRNA isolated from human tissue and 5 pg. ofcRNA were combined and then reverse transcribed into cDNA by usingprimer B (FIG. 13A). The cDNA mixture was then amplified for 25 cycles.Under these conditions, the reaction rates of pE2F cRNA andintron-retention mRNA were identical within an exponential phase of thePCR reaction. Because the exon-skipping mRNA was 135 bp shorter than thewild-type EAAT 2 mRNA, the wild type EAAT 2 mRNA was used as an internalcontrol for the comparative analysis of the exon-skipping mRNA betweenpatients. Using the internal controls as standards, the relative amountsof intron-retention and exon 9-skipping mRNA were calculated andcompared, between patient samples, by densitometric analysis of Southernblots.

For CSF studies, 400 μl CSF was centrifuged (1500×g) for 10 min topellet blood cell debris. Total RNA was isolated from the supernatantusing QIAamp kit (Qiagen). Poly (A) mRNA was further isolated andsubjected to RT-PCR procedures as described above. EAAT 2 is onlyexpressed by CNS tissue. No wild-type or exon 9-skipping EAAT 2 mRNA wasdetected from the pelleted blood cell debris.

PCR products were isolated from agarose gel by using QIAquick GelExtraction Kit (Qiagen). They were then cloned into pCR 2.1 vector (TAcloning Kit, Invitrogen). Plasmid DNA were isolated from transformedcells by using PERFECT prep Plasmid DNA kit (5 prime 3 prime, Inc).Sequencing of the DNA was carried out on an Automated DNA Sequencer(Applied Biosystem).

Primers used for RT-PCR of EAAT 2 were as follows: Primer A(5′-GGCAACTGGGGATGTACA-3′ SEQ ID NO: 14) corresponding to position 933from 5′ translation region; Primer B (5′-CCAGAAGGCTCAAGAAGT-3′ SEQ IDNO: 15) corresponding to position 170 from exon 7-intron junction;Primer C (5′-ACGCTGGGGAGTTTATTCAAGAAT-3′ SEQ ID NO: 16) corresponding toposition 1768 from the 5′ translation region; Primer D(5′-ACCGTCCTCTGCCACCACTCT-3′ SEQ ID NO: 17) corresponding to position−428. Primers used for RT-PCR of EAAT1 were as follows:5′-AGGAGGTTTGGCTTTCTGTGG-3′ (SEQ ID NO: 18 corresponding to position−73; 5′-GGTTTTAACACCTGGTGCTCAA-3′ (SEQ ID NO: 19 corresponding toposition 1655 from the 5′ translation region. Oligonucleotides used forpreparing probe were as follows: 5′-CGGCTGACTITCCATTGGCTG-3′ (SEQ ID NO:20) corresponding to position 1664 from the 5′ translation region ofEAAT 2; 5′-CCTGGTGCTCAAGAAAGTGTTTC-3′ (SEQ ID NO: 21) corresponding toposition 1664 from the 5′ translation region of EAAT 1.

EXAMPLE 2 Aberrant EAAT 2 Transcripts are Present in vivo

To verify that the aberrant EAAT 2 transcripts of Example 1 were presentin vivo and not a cloning or PCR artifact, in situ hybridization wasperformed to detect partial intron 7-retention mRNA using a riboprobe tothe intronic region (FIG. 13A, probe F). FIG. 15A and 3B show that thispartial intron 7-retention mRNA was present only in ALS motor cortex,but not in control specimens, in agreement with the RT-PCR results. Inaddition, signals were uniformly localized to small cells, presumablyastrocytes, present throughout the motor cortex (EAAT 2 is anastrocyte-specific protein) (FIG. 15D; asterisk). As a control, signalsfor actin (FIGS. 15C and F) were found expressed by both neurons(arrowhead) and astroglia. Wild-type EAAT 2 mRNA in ALS (FIG. 15E) andin control tissue were expressed in a distribution similar to thepartial intron 7-retention mRNA. No staining was seen with sensecontrols. Furthermore, the dramatic loss of EAAT 2 protein (Rothstein etal., 1995 supra) (FIGS. 15G and 15H) in ALS motor cortex appears to beassociated with the presence of the partial intron 7-retentiontranscripts, which was specific to ALS and was not detected in motorcortex from control specimens (FIG. 15B), or in specimens of motorcortex from ALS patients that were not RT-PCR positive for theintron-retention transcripts.

In FIGS. 15A to 15H, the partial intron 7-retention mRNA was localizedto small cells throughout the motor cortex in ALS (FIG. 15A), but wasnot detected in control motor cortex (FIG. 15B). When compared to mRNAfor the general cellular protein actin (FIG. 15C), the localizationappeared to be consistent with astrocytes. Higher power analysis (FIGS.15D, 15E and 15F) of ALS motor cortex confirmed that aberrant partialintron 7-retention mRNA was localized to small cortical cells (asterisk,FIG. 15D), identical to the localization of wild-type EAAT 2 mRNA in ALScortical astrocytes (FIG. 15E), whereas actin was localized in bothastrocytes and neurons (FIG. 15F, arrow) in ALS motor cortex. Thelocalization of the partial intron 7-retention EAAT 2 mRNA (FIG. 15A)correlated with the decreased expression of EAAT 2 protein (FIG. 15G) inALS compared with expression of EAAT 2 protein in control motor (FIG.15H) cortex.

In situ hybridization was performed with digoxigenin-UTP labeled RNAprobes generated from 1 μg of DNA template using the Maxiscript In vitrotranscription kit (Ambion, Calif.). The probes for detecting wild-typeEAAT 2 mRNA and the partial intron 7-retention mRNA are indicated inFIG. 13A as probes E and F, respectively. Specificity controls includedsense RNA probes and pre-treatment of tissue with RNase A (10 μg/ml) in2×SSC at 37° C. for 30 min. An actin control provided with the kitcontained −250 bp of β-actin fragment in the antisense orientation.Frozen tissue was sectioned (8 μm), fixed with 4% paraformaldehyde in0.1M phosphate buffered saline (PBS; pH 7.4), rinsed with PBS, treatedwith 0.2% Triton X-100, rinsed again with PBS, followed by proteinase K(1 μg/m) in TE buffer (100 mM Tris-HCl, 50 mM EDTA, pH 8.0) at 37° C.for 30 min, then 0.1 M glycine in PBS, and again with 4%paraformaldehyde in PBS. The sections were acetylated with 0.25% aceticanhydride in TE with 0.1 triethanolamine, rinsed with DEPC water, airdried, then hybridized overnight with probe (2 μg/ml) in hybridizationbuffer (50% deionized foramide, 5×SSC, 10% dextran sulfate, 5× Denhardtsolution, 2% SDS, 100 μg/ml denatured salmon sperm DNA). Thesingle-stranded RNA probe was removed with RNase A (10 μg/ml) at 37° C.for 30 min. The immunological detection of the digoxigenin-labeled RNAprobe was performed using alkaline phosphatase-conjugatedanti-digoxigenin antibody (Boehringer Mannheim) at 1:200 and standardreagents for alkaline phosphatase.

EXAMPLE 4 Nuclease S1 Protection Analysis

S1 nuclease protection analysis of EAAT 2 mRNA (FIG. 16C; describedbelow) also provided evidence that the aberrant splicing EAAT 2transcripts of Example 1 were present in vivo. Northern analysis of EAAT2 mRNA was difficult to use for this purpose because the size of normalEAAT 2 mRNA is about 11 Kb and the truncated transcript would only be˜1-2 Kb smaller. Therefore, it would be difficult to identify thesetruncated transcripts from full length transcript using this method.

FIG. 16C shows an S1 nuclease protection analysis of EAAT 2 mRNA using a836 base single strand DNA probe, located at 3′ end of the codingregion. The protection fragments were subjected to Southern blotanalysis using an oligonucleotide probe located 3′ end of the protectionfragment. As with quantitative RT-PCR, the abnormal species wereabundant in the ALS specimens compared to normal EAAT 2.

S1 nuclease protection assays were conducted as follows. A 836 basesingle strand DNA probe was generated by asymmetry PCR using primer Aand C. PCR conditions are the same as described above except 0.05 μMprimer A and 0.5 μM primer C were used. The expected single strand DNAwas isolated from the gel. For hybridization and S1 nuclease analysis,0.5 pmol of single strand DNA probe was mixed with 1 μg of the mRNAsample and hybridized in a solution containing 80% formamide, 0.4 MNaCl, 40 mM piperazine-N,N′-bis(2-ethanesulfonic acid) (PIPES; pH 6.4),and 1 mM EDTA for 16 hr at 55° C. Samples were then diluted 15-fold withice-cold S1 nuclease buffer (BRL) and treated with 0.5 U of S1 nucleaseper microliter at 25° C. for 1 hr. The protected fragments were resolvedby 1.5% agarose gel electrophoresis and transferred to membrane. Theblot was probed with an oligonucleotide probe located at the 3′ end ofthe protection fragment (described above) and then subjected toautoradiography.

EXAMPLE 5 Quantitative Analysis of Aberrant RNA Processing Products

To determine the abundance of the aberrant mRNA species relative to wildtype EAAT 2, quantitative RT-PCR was performed using mRNA from ALSpatient 4. This patient was chosen because RT-PCR studies revealed onlytwo types of truncated transcripts (FIG. 14C). PCR reaction productsfrom different amplification cycles were resolved by gel electrophoresisand transferred to membrane for Southern blot analysis (FIG. 16A). Theamount of radioactivity recovered from the excised membrane bands wasplotted as function of the number of cycles (FIG. 16B). The rates ofamplification were exponential between 14 and 24 cycles for full lengthand truncated templates. The results revealed that full length(wild-type, wt) and truncated transcripts tr-1, and tr-2 represent 28%,2%, and 70% of total EAAT 2 transcript, respectively. It is notable thatthe truncated transcript tr-2 from this patient is same as thetranscript in FIG. 13B ₇. As described below, this truncated transcriptproduced down-regulation of normal EAAT 2 in vitro. It was found that upto 70% of total EAAT 2 transcripts were aberrant RNA processingproducts.

In FIG. 16B, the amounts of radioactivity recovered from the excisedmembrane bands in (FIG. 16A) were plotted as function of the number ofcycles. The rates of amplification were exponential between 14 and 24cycles for full length and truncated templates. More than 70% of totalEAAT 2 mRNA is in the form of aberrant transcripts.

1. Nuclease Protection Assays

S1 nuclease protection assays were also performed to evaluate therelative abundance of the aberrant mRNA species found in Example 1. A836 base single strand DNA probe, located at the 3′ end of the codingregion was used. The S1 nuclease-resistant fragments were resolved bygel electrophoresis and transferred to membrane. The blot was probedwith an oligonucleotide probe located 3′ end of the protection fragment.As shown in FIG. 4C, large amounts of <836 bp S1 nuclease-resistantfragments were observed in ALS specimens but were not seen in thecontrol specimens. The mRNA sample from ALS patient 4 used in thisexperiment was the same one used for quantitative RT-PCR describedabove. The 346 bp S1 nuclease-resistant fragment, corresponding to thetruncated transcript tr-2, represents 73% of the total protectionfragments, which is in agreement with the quantitative RT-PCR results(FIG. 16B).

EXAMPLE 6 Aberrant EAAT 2 Transcripts Were Present in Sporadic ALS andCorrelated With Loss of EAAT 2 Protein

To evaluate the prevalence of aberrant EAAT 2 transcripts in ALS, 30 ALSspecimens were screened, including spinal cord, motor cortex, andcerebellum for partial intron 7-retention and exon 9-skippingtranscripts by competitive RT-PCR (FIG. 14A). An internal control wasdesigned to amplify along with the partial intron 7-retention mRNA (FIG.13A). Since the exon 9-skipping mRNA was 135 bp shorter than thewild-type EAAT 2 mRNA, the wild type EAAT 2 mRNA was used as an internalcontrol for the comparative analysis of the exon 9-skipping mRNA betweenpatients. All RT-PCR experiments were repeated 2-5 times for eachspecimen to verify the presence of aberrant mRNA species. Both aberranttranscripts were commonly found; 20 of the 30 ALS patients had thepartial intron 7-retention mRNA and 11 of the 30 ALS patients had theexon 9-skipping mRNA. These aberrant mRNA species were only found in ALSmotor cortex and/or spinal cord, but not in cerebellum. To determine thedisease specificity of these aberrant mRNA species, othernon-neurological and neurological disease control tissues were examined(Table 1), including tissue from neuropathogically affected andunaffected regions. The aberrant mRNA species were not found in any ofthe neural tissues from a total of 40 controls, including 27non-neurological disease control specimens (12 spinal cord and 27 motorcortex), 8 spinal muscular atrophy specimens (SMA-type 1) (spinal cord),7 Alzheimer's disease specimens (7 hippocampus and 7 motor cortex), and6 Huntington's disease specimens (6 caudate and 6 motor cortex). Thecontrol tissues were matched for age and postmortem delay (Table 1).Table 1 is shown below. TABLE 1 ALS and control populations used for theanalysis of EAAT 2 mutations. Post-mortem # of Age at death delay (hr)Group patients M/F (mean yr SE) (mean SE) ALS 30  23/7  60.4 2.1  7.30.8 Non-neurological 25  15/19 65.2 2.2 10.4 0.6 disease SMA* 8 3.5  6.61.0 (mo)  9.3 1.8 Alzheimer□s 7 4/3 74.8 2.1  8.2 0.6 diseaseHuntington□s disease 6 2/4 59.3 4.9 11.9 0.7*SMA = spinal muscular atrophy, type 1

In FIG. 17A, identification of both (solid circle) partial intron7-retention and exon 9-skipping mRNA species in the same tissue sampleswas typically associated with a large loss of EAAT 2 protein, while thepresence of partial intron 7-retention alone (solid triangle) or traceamounts of partial intron 7-retention mRNA sequence (open triangle) wasassociated with moderate to little loss of EAAT 2 protein. Absence ofthe abnormally processed mRNA (open square) was associated with normallevels of EAAT 2 protein. In FIG. 17B, the amounts of partial intron7-retention and exon 9-skipping mRNA species in spinal cord and motorcortex were inversely correlated with the amount of EAAT 2 protein.

More particularly, the presence of abnormal mRNA was significantly(P<0.001) correlated with the loss of EAAT 2 protein. ALS specimens frommotor cortex or spinal cord that had very low levels of EAAT 2 protein(<30% of control) contained both partial intron7-retention and exon9-skipping transcripts (FIG. 17A). Eight out of 30 ALS patients had bothpartial intron 7-retention and exon 9-skipping mRNA. An intermediateloss of EAAT 2 protein in neural tissue, 30-80% of control levels, wasassociated with the presence of the partial intron 7-retention mRNAalone. In addition, the loss of EAAT 2 protein was inversely correlatedwith the amounts of either the exon 9-skipping (r_(s)=0.81, P<0.001) orthe partial intron 7-retention mRNA (r_(s)=0.62, P<0.001; FIG. 17B).Although the presence of aberrant mRNA species appeared to correlatewith a loss of protein, rarely patients with a loss of EAAT 2 did nothave either of these aberrant mRNA. In those cases, the loss of proteincould be due to other, as additional variants in EAAT 2 mRNA.Alternatively, other mechanisms known to lead to degradation ofglutamate transporter proteins, e.g. oxidative stress, could haveresulted in a loss of EAAT 2 (Trotti et al. (1996) J. Biol. Chem. 271,5975; Volterra et al. (1994) Mol. Pharmacol, 46, 986).

The presence of the aberrant mRNA species did not correlate with theclinical presentation (spinal versus bulbar onset) of the disease in ALSpatients. ALS patients with altered EAAT 2 mRNA species had a tendencytoward shorter survival (17±2.9 (SEM) months) when compared to theoverall average for ALS of 2-5 years (Kuncl et al. (1992). Motor neurondiseases. In diseases of the Nervous System, A. K. Asbury, G. M.McKhann, and W. I. McDonald, ods. (Philadelphia: W. B. Saunders). pp.1179-1208). But not when compared to the ALS patients in this studywithout aberrant mRNA species (23±4.8 (SEM) months).

EXAMPLE 7 Detection of Aberrant EAAT 2 Transcripts in CerebrospinalFluid

Cerebrospinal fluid (CSF) was also examined for the presence of the exon9-skipping transcript in ALS and control specimens (FIG. 14B). Allspecimens were processed identically. Control CSF was obtained frompatients with neurological diagnoses that included: multiple sclerosis,normal pressure hydrocephalus, hepatic encephalopathy, migraineheadache, subarachnoid hemorrhage, stroke, epilepsy, ataxia, CNSvasculitis, and dementia. The exon 9-skipping mRNA was not detected inthe 38 control specimens, but was detected in 12 out of 18 (66%) ALSspecimens. In addition, in four ALS cases (Table 2), CSF obtained duringdiagnostic evaluation and brain tissue obtained at autopsy wereavailable from the same patients. In those patients, CSF was collected25.5±6 (SEM) months prior to death. In all cases, the presence of theexon 9-skipping mRNA was detected in both ante-mortem CSF andpost-mortem brain or spinal cord tissue.

FIG. 14B showed that the exon 9-skipping EAAT 2 mRNA is present in someALS cerebrospinal fluid specimens. FIG. 14C showed RT-PCR for fulllength EAAT 2 reveals multiple truncated transcripts in ALS but not incontrols. The aberrant species were present in motor cortex, but notcerebellum (Cblm) or hippocampus (Hipp).

Table 2 is shown below. TABLE 2 Exon-9 skipping EAAT 2 species arepresent in ALS CSF prior to death: Examination of CSF and post mortembrain specimens. Exon 9-skipping Disease CSF collection: time EAAT 2 AgeDuration before death (RT-PCR) Patient (at death) (mo) (mo) CSF Brain 144 39 27 + + 2 52 46 41 + + 3 62 15 12 + + 4 63 22 22 − −+ exon 9-skipping EAAT 2 present in sample;− exon 9-skipping species not detectable.

EXAMPLE 8 Proteins Translated from Aberrant Transcripts are Unstableand/or Cause Down-Regulation of Normal EAAT 2 in vitro

To determine if proteins translated from these aberrant EAAT 2transcripts could be identified in the ALS post mortem tissue, ALS motorcortex was analyzed for a carboxy-terminal truncated EAAT 2 protein (thepresumed protein product of the partial intron 7-retention transcript)by Western blotting with amino-terminal oligopeptide antibodies to humanEAAT 2 protein (Rothstein et al., 1995 supra). Previous studies haveshown that the amino terminal antibody can recognize wild-type EAAT 2 inhuman tissue. However, using this antibody, no immunoreactive band withthe expected size of the truncated EAAT 2 protein was detected. Theprotein from the exon 9-skipping transcript was also investigated in ALStissue, using oligopeptide antibodies to the amino acid sequencespanning the deletion site. Again, no immunoreactive band was detected.The inability to detect the aberrant EAAT 2 proteins could be due to atleast two possibilities: 1) the aberrant EAAT 2 transcripts could bevery unstable and/or rapidly degraded in post mortem tissue, or 2) maynot be detectable with the available antibodies. They also may affectnormal EAAT 2 function.

1. Glutamate Transport Assays

To evaluate the properties of these abnormal transcripts, EAAT 2 cDNAwas transiently expressed in COS7 cells. EAAT 2 protein was quantitated72 hours post-transfection by Western blotting and activity of thetransporter was measured by a sodium-dependent, ³H-glutamate transportassay (Rothstein et al. (1992) N. Engl. J. Med. 326, 1464; Rothstein etal., (1995), supra). Wild-type EAAT 2 protein was detected by acarboxy-terminal EAAT 2 antibody (FIG. 18A, lane 1) as well as evidenceof glutamate transport. Wild-type EAAT 2 was not detected by theavailable amino-terminal antibody. As expected, predicted truncatedprotein synthesized from the partial intron 7-retention cDNA was notdetected by this carboxy-terminal antibody (FIG. 18A, lane 5).Nevertheless, there was evidence that the partial intron 7-retentionEAAT 2 cDNA was expressed by the COS7 cells because the partial intron7-retention mRNA was detected in the transfected cells by Northernblotting and RT-PCR. No glutamate transport was observed in COS7 cellstransfected with the partial intron 7-retention cDNA.

When the partial intron 7-retention cDNA was co-transfected with thenormal EAAT 2 cDNA into COS7 cells, there was a progressive decrease inthe level of normal EAAT 2 protein (FIG. 18A, lanes 2-4). However, thelevels of wild type EAAT 2 mRNA, using Northern analysis, were notdeceased by the partial intron 7-retention cDNA (FIG. 18A, lanes 2-4).Glutamate transport also decreased in parallel with the loss of EAAT 2protein (FIG. 18A, lanes 2-4). The same results were obtained when thepartial intron 7-retention cDNA was co-expressed in HeLa cells (FIG.18A, lanes 6-7). These co-expression studies suggest that the partialintron7-retention cDNA could dominantly down-regulate EAAT 2 protein.This effect was specific for EAAT 2; co-expression of theintron-retention cDNA with wild-type EAAT2, EAAT3 or EAAT4 cDNA had noeffect on either the astroglial subtype EAAT1 (FIG. 18A, lanes 8 and 9),or the neuronal subtypes EAAT3 and EAAT4 protein or glutamate transport.This effect is not due to the promoter competition between wild type andpartial intron 7-retention cDNA because (i) the levels of wild type EAAT2 mRNA were not decreased and (ii) this effect was not observed in othersubtypes of glutamate transporters with the same vector and transfectionconditions.

The exon 9-skipping EAAT 2 cDNA was also expressed in COS7 cells.Although the protein was not detected by Western blotting (FIG. 18B,lane 2), the mRNA was detected in the transfected COS7 cells by RT-PCR.However, no glutamate transport was observed in the transfected COS7cells by sodium-dependent,³H-glutamate transport assay. Notably, in thisparadigm, the exon 9-skipping cDNA had no effect on the expression ofwild-type EAAT 2 protein or glutamate transport (FIG. 18B, lane 3).

As noted, FIGS. 18A and 18B depict transient expression of the partialintron 7-retention and exon 9-skipping EAAT 2 cDNA in COS7 cells and inHeLa cells. Different combinations of indicated plasmids weretransfected into COS7 cells (FIG. 18A, paradigm 1-5 and 8-9; FIG. 18B,paradigm 1-3) or HeLa cells (FIG. 16A, paradigm 6-7) by electroporation.After 72 hours, some transfected cells were used to quantitate expressedEAAT 2 or EAAT1 protein by immunoblotting using carboxy-terminaloligopeptide antibodies to EAAT 2 or EAAT1 protein, or EAAT 2 mRNAexpression by Northern blot. Others were used to measure functional EAAT2 or EAAT1 by sodium-dependent, ³H-glutamate transport assay. (FIG.18A). The partial intron 7-retention EAAT 2 cDNA produced a negativeeffect on the normal EAAT 2 protein level and glutamate transport(paradigm 1-7), but had no effect on EAAT 2 mRNA levels (paradigm 1-5),EAAT1 protein levels (paradigm 8,9) or EAAT1 glutamate transport(paradigm 8,9).

In FIG. 18B, the exon 9-skipping EAAT 2 species had no effect on EAAT 2protein expression (paradigm 3) or on wild type glutamate transport(paradigm 3). All aberrant or wild-type EAAT 2 (EAAT1) cDNAs were in thesame vector (pcDNA3).

Several mechanisms could account mutant protein interference withwild-type EAAT 2 activity. More information can be learned aboutglutamate transporter membrane organization or trafficking. Some datasuggests that under normal conditions, EAAT 2 monomers mayself-associate to form homomeric multimers in vivo (Haugeto et al.(1996) J. Biol. Chem. 271, 27715). Without wishing to be bound to anyspecific theory, it appears that heteromers composed of mutant truncatedEAAT 2 and wild-type EAAT 2 protein subunits undergo rapid degradation.This theory could explain the loss of EAAT 2 in COS7 cell expressionexperiments and in ALS. Examples of such dominant-negative interactionsbetween multimeric proteins is not uncommon. For example, in mice, aretained intron for the vitamin D receptor, leads to a truncatedprotein; this protein subsequently forms heterodimers with retinoic acidreceptors, ultimately dominantly down regulating vitamin D signaling(Ebihara et al. (1996). Mol. Cell. Biol. 16, 33393).

2. Aberrant EAAT 2 cDNA Expression and Translation in Cells

To confirm that the aberrant EAAT 2 cDNAs were expressed and translated,we constructed chimeric genes to encode C-terminal fusions of wild-typeor mutant EAAT 2 to green-fluorescent protein (GFP). These constructswere expressed in COS7 cells and all produced similar levels of mRNA byNorthern blotting. The wild-type EAAT 2-GFP transfected cells had normal³H-glutamate transport activity when compared to non-GFP EAAT 2transfected cells. Expression of fusion proteins was examined by Westernblotting using anti-GFP antibodies (FIG. 19A). Both the partial intron7-retention (FIG. 19A, lane 3) and the exon 9-skipping (FIG. 19A, lane4) EAAT 2-GFP proteins were expressed at the expected lower molecularweights. Furthermore, the mutant EAAT 2-GFPs appeared to be unstablecompared to the wild-type EAAT 2-GFP (FIG. 19A, lane 2) as judged by thepresence of less protein and multiple lower molecular weight species(FIG. 19A, lanes 3 and 4).

As noted above, FIG. 19A is an immunoblot of COS7 cells expressing EAAT2-GFP fusion protein using anti-GFP antibody. Lane 1, pEGFP vector; lane2, wild-type EAAT 2-GFP; Lane 3, partial intron 7-retention EAAT 2-GFP;Lane 4, exon 9-skipping EAAT 2-GFP; lane 5, COS7 cells alone. Thepartial intron 7-retention and exon 9-skipping mRNA produced truncated,unstable proteins.

2. Cellular Localization of Aberrant EAAT 2 Fusion Proteins

The cellular localization of the fusion proteins was then examined byfluorescent microscopy. Wild-type EAAT 2-GFP was preferentiallylocalized to the cell surface (FIG. 19C). However, both the partialintron 7-retention and the exon 9-skipping EAAT 2-GFP fusion proteinswere restricted to the cytoplasm, often peri-nuclear (FIG. 19D-E) andoccasionally in lysosomes. When wild-type EAAT 2-GFP was co-expressedwith the partial intron 7-retention EAAT 2 (not GFP-labeled), thewild-type protein was found largely confined to the cytoplasm, withoccasional cell membrane staining (FIG. 19F). The same results wereobserved from co-expression of partial intron 7-retention EAAT 2-GFPwith wild-type EAAT 2 (not GFP-labeled) (FIG. 19). These results suggestthat the partial intron 7-retention EAAT 2 protein may interfere withnormal EAAT 2 protein complex assembly or trafficking. These resultswere not seen with the exon-9 skipping EAAT 2, which did not interferewith wild-type EAAT 2 localization (FIG. 19G). Importantly, the abnormalprotein localization is probably not due to the influence of the GFPfusion because (i) wild-type EAAT 2-GFP transfected cells had normalglutamate uptake, (ii) the wild-type-GFP protein was localized on thecell surface when expressed alone or with the exon-9 skipping EAAT 2(FIG. 19), and (iii) the partial intron 7-retention EAAT 2 (notGFP-labeled) still interfered with the wild-type EAAT 2 proteintrafficking to the cell membrane.

As noted, FIG. 19B-19I show a normal and aberrant EAAT 2 protein in COS7cells. COS7 cells expressing GFP, wild-type EAAT 2-GFP, partial intron7-retention EAAT 2-GFP, or exon 9-skipping EAAT 2-GFP proteins wereexamined by fluorescent microscopy. Aberrant proteins (exon-9skipping-GFP, partial intron-7-retention-GFP expressed alone or withwild-type EAAT 2) were largely confined to the cytoplasm, compared tonormal surface membrane localization of EAAT 2. A co-expression of theGFP-labeled EAAT 2 with the unlabeled partial-intron-7-retention EAAT 2revealed that the aberrant protein interfered with the localization ofwild type protein in the surface membrane. All transfection experimentswere repeated five times in triplicate. ³H-glutamate transport expressedas mean transport+SE compared to control.

Eight other aberrant cDNAs were also expressed (described in FIG. 13B)in COS7 cells. Two of them, shown at FIGS. 13B ₄ and 13B₇ also showed adominant down-regulation effect on normal EAAT 2 activity and proteinexpression, like the partial intron 7-retention EAAT 2 cDNA, while theremaining cDNAs were unstable and inactive, like the exon 9-skippingEAAT 2 cDNA.

Immunoblots were performed as described previously (Rothstein et al.,(1995) supra) on 4-25 μg of crude homogenate from motor cortex or fromhomogenized transfected COS7 cells grown on 75 mm plastic culture plates(CoStar), with affinity-purified polyclonal antibodies to thecarboxyl-terminal region of EAAT 2 (Rothstein et al., (1995) supra) orto green fluorescent protein (GFP) (1:2000; Clontech). Glutamatetransport was measured as described (Rothstein et al., (1992) supra)except using intact COS7 cells grown on 30 mm, 6 well plates (CoStar).

Wild-type as well as aberrant cDNA fragments were cloned into aeukaryotic expression vector (pcDNA3). The constructed plasmids werethen transfected into COS7 cells or HeLa cells by electroporation.Electroporation (Bio Rad “Gene Pulser II” 300V at 500 μF) was performedon 1×10⁷ cells in a solution of DMEM containing 500 μg of salmon spermDNA along with the pcDNA3 plasmid containing the transporter subtype.

For construction of EAAT 2-GFP fusion gene, wild-type or aberrant EAAT 2cDNA in pcDNA3 was amplified by PCR using (+) strand T7 primer and (−)strand primer (for wild-type and exon-skipping mutant using5′-GGATCCCGGGCCCTTTCTCACGTTTCCAAGG-3′ (SEQ ID NO: 22); for partialintron7-retention species using 5′-GGATCCCGGGCCCCCTGGAAGCGGTGCCCAG-3′(SEQ ID NO: 23). To create a restriction site for cloning purposes, weadded a 13 sequence (shown underlined) at 5′-ends of the primer tocreate Apa I. The resultant PCR products were digested with EcoR I andApa I and then cloned into the N-terminus of GFP gene in pEGFP-N2 vector(Novagen). Sequences of the chimeric genes were checked at their fusionsites.

In general, examples 1 to 8 show that loss of EAAT 2 protein in ALS isdue to aberrant EAAT 2 transcripts. In particular, functional glutamatetransport was found to be deficient in ALS and a substantial proportionof patients with sporadic disease were found to have a large loss of theEAAT 2 glutamate transporter protein. Without wishing to be bound to anyparticular theory, the examples indicate that the loss of EAAT 2 proteinin ALS is due to aberrant EAAT 2 mRNA and is a consequence of abnormalRNA splicing.

Significantly, the aberrant EAAT 2 mRNAs described in the examples wererestricted to motor cortex and spinal cord, the primary regions ofneurodegeneration. Loss of EAAT 2 or the presence of aberrant EAAT 2mRNA species in a subset of ALS patients was not found. All of thepatients had pathological confirmation of motor neuron loss. Neitherwere they found in other neurodegenerative diseases, such as SMA,Alzheimer's or Huntington's disease, which are also characterized byslow loss of neurons (including motor neurons) and astrogliosis. But seeExample 9 below. The aberrant mRNA species were also detected in patientcerebrospinal fluid up to 4 years prior to death. The subsequent loss ofEAAT 2 could act to propagate motor neuron degeneration in ALS. Theclinical efficacy of anti-glutamate drugs in ALS and transgenic modelsof ALS (Bensimon et al. (1994) N. Engl. J. Med. 330: 585; Gurney et al.(1996) Ann. Neurol. 39, 147; Lacomblez et al. (1996) Lancet 347: 1425)support the notion that glutamate-mediated toxicity, in part due to theloss of EAAT 2, can contribute to the pathogenesis of ALSAccordingly,the aberrant mRNA species are not a result of motor neuron loss orpost-mortem artifact.

EXAMPLE 9 Detection of Aberrant mRNA EAAT 2 mRNA Transcipts in AD

Aberrant EAAT 2 transcripts were not found in about seven (7)Alzheimer's disease specimens including hippocampus (typically, the mostaffected area in AD) and motor cortex. However, aberrant EAAT 2transcripts could be found in the frontal cortex of AD patients. It isrecognized that the frontal cortex is also affected in AD. The aberrantEAAT 2 transcripts discovered include the partial intron 7-retentionsequence. See FIG. 2 and SEQ ID NO: 3. It is believed that the aberrantEAAT 2 transcripts are also present in at least some AD patients. A lossof EAAT 2 protein has been found in some AD patients. See J. ofNeuropath. and Experimental Neurol. 56: 901.

The invention has been described in detail with reference to preferredembodiments thereof. However, it will be appreciated that those skilledin the art, upon consideration of this disclosure, may make modificationand improvements within the spirit and scope of the invention as setforth in the following claims.

1. A method of detecting a neurological disorder in a patient, themethod comprising obtaining a biological sample from the patient; anddetecting at least one aberrant human glutamate transporter 2 (EAAT 2)mRNA in the sample as being indicative of the neurological disorder inthe patient.
 2. The method of claim 1, wherein the neurological disorderis associated with excitotoxicity.
 3. The method of claim 1, wherein theneurological disorder affects motor neuron function.
 4. The method ofclaim 1, wherein the neurological disorder is amyotrophic lateralsclerosis (ALS), Huntington's disease (HD), Parkinson's disease (PD), orAlzheimer's disease (AD).
 5. The method of claim 1, wherein the samplecomprises fluid obtained from the central nervous system (CNS) of thepatient.
 6. The method of claim 5, wherein the fluid is cerebrospinalfluid (CSF).
 7. The method of claim 1, wherein the method furthercomprises amplifying the aberrant human glutamate transporter 2 (EAAT 2)mRNA by a polymerase chain reaction (PCR) sufficient to make cDNA fromthe mRNA.
 8. The method of claim 7, wherein the PCR is a reversetranscriptase-PCR reaction (RT-PCR).
 9. The method of claim 7, whereinthe method further comprises determining a DNA sequence from the cDNA.10. The method of claim 9, wherein the DNA sequence is substantiallyhomologous to a DNA sequence shown in any one of SEQ ID NOs. 3 and 5-13or the complement thereof.
 11. The method of claim 10, wherein the DNAsequence is identical to any one of SEQ ID NOs. 3 and 5-13 or thecomplement thereof.
 12. The method of claim 1, wherein the methodfurther comprises making a cDNA library from the sample, and detecting acDNA in the library comprising DNA sequence substantially homologous tothe aberrant human glutamate transporter 2 (EAAT 2) mRNA.
 13. The methodof claim 12, wherein the DNA sequence of the cDNA is substantiallyhomologous to any one of the SEQ ID NOs. 3 and 5-13 or the complementthereof.
 14. The method of claim 12, wherein the DNA sequence of theeDNA is identical to one of the SEQ ID Nos. 3 and 5-13 or the complementthereof.
 15. A method of isolating an aberrant human glutamatetransporter 2 (EAAT 2) cDNA, the method comprising: a) obtaining abiological sample from a patient having or suspected of having aneurological disorder, wherein the sample comprises mRNA, b) producingcDNA from the sample, the cDNA comprising DNA sequence substantiallyhomologous to any one of SEQ ID NOs. 3 and 5-13 or the complementthereof, c) introducing the cDNA into test cells under conditionssufficient to express the cDNA in the test cells; and d) detecting areduction in glutamate transport in the test cells compared to controlcells expressing a normal human glutamate transporter 2 gene or cDNA asindicative of isolation of the aberrant human glutamate transporter 2(EAAT 2) cDNA.
 16. The method of claim 15, wherein the sample comprisesnervous system tissue obtained from the patient.
 17. The method of claim15, wherein the neurological disorder is associated with excitotoxicity.18. The method of claim 15, wherein the neurological disorder is a motorneuron disorder.
 19. The method of claim 15, wherein the neurologicaldisorder is amyotrophic lateral sclerosis (ALS), Huntington's disease(HD), Parkinson's disease (PD), or Alzheimer's disease (AD).
 20. Themethod of claim 15, wherein the cDNA from the sample comprises sequencesubstantially homologous to the sequence of SEQ ID NOs. 3 and 5-13 orthe complement thereof.